Don Abbott



From the time the first paratrooper hit the inhospitable ground of the Island of Corregidor, early on the morning of 16 February 1945, the men of the 503rd Parachute Regimental Combat Team had heard the sound of explosions and felt the  ground shake from the  resulting concussion.  These explosions  began early in the operation with B-25 and A-20 aircraft plastering areas outside the  drop zones with 500 pound bombs even while the men were in the air.

These planes also spread a smoke screen to keep Japanese troops in the Eastern part of the Island from spotting the men dropping from the sky in their parachutes.

As the days progressed, the men of the 503rd became conditioned to hearing bombs,  grenades and explosions set off by demolition teams seeking to close up bunkers containing Japanese Imperial Marines who could not be flushed out and who rejected any suggestion of capitulation.

Most of the explosions, while not inconsequential, were confined to localized areas.  There had been a few spectacular blasts, such as the one which went off inside Malinta Tunnel on the night of 21-22 February.  That one shook the island and sent blow-torch-like flames bursting from every entrance to the huge underground system.

But it was the catastrophic detonation of 26 February which set a new standard for magnitude.  People outside the 59th Coast Artillery Barracks at Topside when the blast occurred were nearly blown off their feet by the concussion even though they were located over two miles from the explosion.  Although the epicentre was out of sight because Malinta Hill and several buildings at Topside intervened, the plume of smoke and debris could, clearly, be seen rising several thousand feet into the air.  It was later learned large rocks landed on the deck of a Navy destroyer standing off shore over a mile from the explosion.

The 503rd had been fighting on Corregidor for more than a week.  The Western portion of the Island had been a killing field for thousands of Japanese troops who had died rather than surrender to inevitable defeat.  Combat there, though still rough, had pretty much settled down to mopping up operations.  On 24 February, the First Battalion of the 503rd attacked through the 3rd Battalion of the 34th Infantry at Engineers Point with the objective of seizing all the ground on the tail of the Island from the Japanese.  The Third Battalion of the 503rd followed and mopped up pockets of resistance bypassed by the First Battalion.  The Second Battalion was left to continue the dirty job of digging out and eliminating remaining Japanese still fighting on the head of the Island, including ''Topside''.

Heavy fighting was experienced as the First Battalion battled its way along Water Tank hill toward the tail of the Island but by the night of 25 February the Paratroopers occupied a line on high ground extending from Cavalry Point on the North to Monkey Point to the South.  The line overlooked Kindley Landing Field and the tail was in sight.  To the East the Island narrowed to a few hundred yards wide.  The Japanese defenders were being concentrated, much as if they were fish in a pocket seine.  Some of the Japanese attempted to swim to the Bataan Peninsula which is not much over two miles away at that point. But that was a high risk venture because even if the swimmer could conquer the swiftly flowing currents, there were LCM's and PT Boats patrolling the channel.  The Japanese defenders of Corregidor were getting desperate.

Monkey Point was the location of the Navy Intercept Tunnel, also known as Station ''C'' or Tunnel ''Afirm''.  A little background on that installation is needed to appreciate the story which follows.  In the early 1930's the US Navy established at least two locations to intercept radio communications of the Japanese Imperial Navy.  Earlier the Japanese Naval Code had been broken and through the use of ''Purple Machines'',  to the extent the U S Navy was able to decipher a good deal of  Japanese coded message traffic.  The locations, at first, included Guam and Shanghai, China which were equipped with '' Purple Machines''.  As the Japanese invasion of China brought fighting closer to Shanghai, the Intercept Station there was moved to the Philippines.  Station ''C" as it was called, was first moved to Olangapo at Subic Bay.  Radio reception there, unfortunately, was not favorable because the surrounding hills interfered.  Consequently, Station "C'' was moved to Marivales and, later, Cavite Naval Base on the Southern shores of Manila Bay.  Here the reception was better but the many large electric motors used in the Naval Repair facilities caused serious interference.  The station needed to be moved again and the choice was now a site on Corregidor.  The Army, which had supreme control over operations on Corregidor, discouraged the move because they had plans to install a Radio Direction Finding Station of their own and they feared the Naval installation would interfere with that operation.  The Army was less than enthusiastic about the Navy locating on its Island of Corregidor because Naval personnel were given much better quarters, had better food and, in general, had higher  ratings so their pay was better than the run-of-the-mill Army man.  The Navy unit operating Station ''C'' was manned with exceptionally intelligent people, needed to operate the high tech facilities, and they demanded comparable perquisites.

Regardless of the Army intransigence a construction program for the Navy was begun on Corregidor.  Project Afirm, for the letter ''A'', was the digging of the intercept tunnel near Monkey Point.  Project Baker, for the letter ''B'', was the installation of the Navy High Frequency Direction Finder station on the tail of the Island.  Project ''Cast'', for the letter ''C'' undertook the construction of quarters for the Naval personnel not far from the Intercept Tunnel.  Station ''C'' was moved to the Island in October, 1939 and it occupied the newly completed tunnel.

As the siege of Corregidor began soon after the Japanese attack on Pearl Harbor in December, 1941, the Army settled down to hold out on Bataan and Corregidor as long as they possibly could, assuming the United States would send reinforcements.  The personnel at the Navy Intercept Tunnel, on the other hand, began to be removed from the dangerous location as fast as the Navy could arrange for submarine transportation.  These highly trained people had an extremely important role to play in monitoring Japanese secret communications which made it imperative they (1)  should not fall into Japanese hands as Prisoners of War and (2)  be moved so they could continue their operations elsewhere.  Station ''C'' personnel provided information about Japanese Naval operations which made possible US Navy victories in the Coral Sea and at Midway, for example.  The last of the personnel from Station ''C'' were evacuated during March 1942, well ahead of the surrender of Corregidor on 6 May 1942.

Now to return to events taking place during the Liberation of the Island of Corregidor in February 1945.

As the 503rd’s First and Third Battalions approached the Navy Intercept Tunnel the Navy facility was not difficult to spot because of the virtual forest of at least twenty antenna poles surrounding the site.  These poles, some foot and a half in diameter and 30/40 feet high were a dead give-away.

On the morning of  26 February, as the First Battalion was  getting ready to resume their attack to the East,  a huge explosion went off in the Navy Intercept Tunnel. 



The actual cause of that explosion will, undoubtedly, never be known for certain.  What is known is that a very large supply of high explosives was set off.  People who were close to the site at the time have two somewhat different theories.  One is that the Japanese, occupying the tunnel, chose to commit suicide by setting off the explosion, thereby taking many of the Paratroopers with them.  This was not an inconceivable concept considering the Japanese had not hesitated to do the same thing in other locations, but on a much smaller scale.  The other version, and the one which seems more likely, is that the explosion was set off accidentally by the tank, sitting on a small mound near the Main Entrance firing into the mouth of the tunnel.  The  force of the  explosion was such that the tank was blown into the air and landed upside down.  Whichever version is correct there is no doubt but what the explosion was a catastrophic event.  Available records give the number of casualties for 26 February but do not break out those due to this event alone.  It appears, however, there were about 30 Paratroopers killed outright and about 125 seriously injured.  The real number of injured will never be known since a number of men with cuts and bruises, which would have been considered seriously disabling under other circumstances, did not seek help because they knew others needed help much more than they.


Japanese Deat after the explosion at Monkey Pt.

An unknown, but substantial, number of Japanese troops were killed.


Many stories of the survivors of the explosions abound.  Captain Bill Bossert, Company Commander of  “A” Company was talking on his walkie-talkie with 2nd Lt. Rene Stievenart who was sheltered behind the tank  firing into the entrance of the tunnel.  Stievenart was killed instantly as the tank rolled over him.  The tank  crew, except for one man, Guy Crull, was also killed.  Debris from the explosion nearly covered Bossert.  The rocks included in the debris pounded down on him and crushed his ribs.  Luckily, some of the other men spotted his plight and came to his rescue, digging him out from the covering debris.

Pfc Carl Bratle happened to be located beside one of the radio antenna poles when the explosion occurred.  He could see all the rocks, dirt and rubble in the sky and knew he needed cover to protect him  when it came down.  He dropped his M-1 and hugged the pole and made himself as compact as he could.  Fortunately, most of the stuff missed him.  A rock landed on his rifle, however, smashing the wooden stock .

Conventional wisdom over the years since 1945 has been that the Navy Intercept tunnel was completely destroyed on that morning of 26 February 1945.  A man, the ''foremost authority on Corregidor'' (according to a writer for the National Geographic Magazine) guided  visitors to the middle of a large field of Cogan grass.  Immediately to the West of a handball court which is a very prominent landmark near Monkey Point, he tells them ''this was the location of the Navy Intercept Tunnel before it blew up''.  He goes on to explain that the explosion was so fierce the area had all the soil skinned off and trees will never grow there.  


The Handball Court at Monkey Pt., Corregidor.

Looking to the North and East of the handball court a hillside is covered with jungle growth which, when left uncleared or unburned for a season or two,  looks too formidable and difficult to explore.


The only available, detailed, large-scale map of the area, updated through 1936, gives no details of the Navy Intercept Tunnel since the tunnel complex was not begun until after 1938 and was completed in 1940.  In the area involved, the 1936 map shows a road leading to Kindley field but no other man-made installation near by.

A retired Navy Captain Duane Whitlock was contacted to see if he could shed any light on the location of the Navy Intercept Tunnel.  He had served there as an enlisted radio man during the early days of the Siege and had been evacuated by submarine around the middle of March 1942, as were all the other Navy people serving in the tunnel.  This veteran was located through the Naval Cryptologic Veterans Association.  That organization compiled a booklet of reminiscences in 1983, a copy of which can be found in the Library of Congress in Washington, DC. Under the  title INTERCEPT STATION ''C'' from Olongapo through the evacuation of Corregidor 1929-1942.  One of the key questions asked of this veteran was if he recollected where the entrance to the tunnel was located in relationship to the handball wall.  He remembered there was a Navy Lieutenant who was a handball enthusiast and that a handball court had been built for him.  He also recalled walking from his quarters to the entrance to the tunnel and seeing the handball court on his right.  He remembered the tunnel was not far beyond the court.

The field of Cogan grass, in the area near the handball court, was explored with the information provided by Captain Whitlock.

Just to the North of the handball court  evidence pointed to the existence of a road leading past it and continuing to the East.  It was over grown with grass, bushes and trees.  If it had not been known to exist it would have been very easy to pass over without notice.  Following the trace of the road a few yards a concrete wall about five feet high and, perhaps, twenty feet long was found.  Upon closer inspection a second retaining wall could be seen.  The wall on the right, facing West, was standing.  The one on the left, had fallen, or had been blown down and nearly covered what had been a concrete ramp.  

This,  certainly, seemed to be what was left of the Main Entrance to the Navy Intercept Tunnel! Opposite the entrance, looking to the South, stood a mound of earth and stone, 10 to 15 feet high where the tank, firing into the entrance, was spotted before the explosion.

Directly to the North of the ramp, between the two walls, was a large crater.  This could only be seen after the energetic use of a bolo to clear away some of the heavy vegetation choking the crater.  It was larger than any of the 1000 pound bomb craters which can be seen around Topside.  It was in the range of 50 to 60 feet in diameter.  It appeared conventional information was right:  the Navy Intercept Tunnel had been completely obliterated in 1945.

A few feet off the road leading to Kindley Landing Field is one of the best examples of a Panama Mount left anywhere on Corregidor.  This particular mount covers a full 360 degree traverse and has not been touched by scrappers after the railroad rail around its Perimeter.  The 155 mm howitzer position may have been part of Battery Levagood, one of the Batteries manned by the 92nd coast Artillery, Philippine Scouts.  Since many of the Batteries had more than one gun position a search for more Panama Mounts was begun.  Nearby were the ruins of a building which had been constructed of stones held together by cement.  The building had been pretty well blasted but it may have been some sort of magazine or shelter relating to Battery Levagood.  Continuing on a few yards to the West another blasted structure was found. This one had two concrete walls leading down at about a 45 degree angle for about 30 feet.  It looked like the walls of a stairway.  The significance of this facility was not immediately clear.  Continuing to beat around the mixed cogan grass/brushy area just to the North of the Topside-Kindley Field Road a huge hole in the surface comes in view.  Care must be taken not to fall in.  The hole is about 15 feet in diameter.  A rock tossed into the hole seems to take forever before hitting the bottom.  Laying against one side of the hole is what appears to be a concrete air shaft.  A flashlight on a cord lowered down the shaft reveals a depth of about 45 feet!  Putting together some of what had been learned from the Cryptological Association book and what could be seen on the ground:  (1) the walls down the hill appeared to be the Main Entrance to the Navy Intercept Tunnel, (2) the two walls leading downward at a 45 degree angle seemed to the ''Exit, 100 steps'' shown on the Cryptological Association stylized drawing of the tunnel and (3) it seemed logical to assume there would be an air shaft even if it had not been shown on the stylized drawing.  It became clear these all must be part of the tunnel which was thought to have been obliterated.

The hole, or void, around the air shaft is a mystery but one guess of how it could have been made has some merit.  A hole must have been dug from the surface down to the tunnel below.  Forms were built to form an air shaft and concrete poured.  Afterward dirt must have been back-filled to fill the void.  This dirt would be weaker, or less compact, than the ground around it.  The huge explosion on 26 February 1945, looking for relief must have ejected the back-filled earth like a volcanic eruption .  That must have been a sensational sight!  (Except that you would have stood a good chance to have died from concussion to see it. - Ed) 


Although the entrance, the two walls leading down and the air shaft appeared to have been part of the Navy Intercept Tunnel, there were some problems, however, in fitting the parts together since the two walls leading down were a long way from the Main Entrance down the hill.  The Navy Captain had said the whole tunnel was about  150 to 200 feet long.  If these were three parts of the navy Intercept Tunnel it was hard to visualize how they fit.

At the walls leading down (the ''Exit'') a closer look at the bottom of the caved in portion showed two small holes, perhaps six inches in diameter, on the opposite sides of a large boulder.  Several days later these finds were shown to a visitor.   He was a sinewy fellow from Los Angeles who is nearly a professional explorer and adventurer, travelling to many parts of the world seeking interesting experiences.  He began digging around the boulder with his survival knife until he dislodged it.  It dropped down the hole and could be heard rumbling for a scary length of time before it came to a crashing stop.  This hole was part of a lot larger open area below.  He continued to enlarge the hole until he could get his head in with a flashlight.  He could see a good deal of space below.  The hole was further enlarged until it was just large enough for his slim body  to slip through.  Using a 30 foot rope to belay him, he disappeared down the hole. He was gone for, probably, a half hour.  When he returned he had several pieces of human bone, a rubber Japanese shoe sole and a leather shoe sole which seemed too large for a Japanese person. Underground facilities always raise a question of whether  there is enough air for a person to, safely, explore.  When asked about the air in the hole the explorer said there was lots of fresh air since he had been all the way  to the air shaft and that the shaft  around the hole provided lots of air.  Surprisingly, he said there was no way to get into the air shaft from the void around it.

After nearly a month,  exploration of the area around the Navy Intercept Tunnel at Monkey Point came to an end for 1989.  All of these thoughts remained.  What had actually been found?  Was this all, really, a part of the Navy Intercept Tunnel or was it something else?  How extensive was the tunnel?  Was it possible for someone, not as agile as the fellow from Los Angles, to get into and explore the Tunnel?

In April 1990 the writer and Ed McCarthy returned to Corregidor to make a video tape.  The purpose of the project was to tape facilities on the Island before they were  further destroyed by ''scrappers'' and the passage of time.  Ed  was born on Corregidor prior to World War II while his father was a high ranking non-commissioned officer stationed at the headquarters of Fort Mills.  Ed retired from the Navy in 1989 as a Chief Warrant Officer.  He had been on active duty, stationed at Subic Bay flying drones.  Later he worked for a civilian contractor and lived on Luzon performing the same job he had while in the service.

Although Ed was very familiar with Corregidor, he knew little about the Navy Intercept tunnel at Monkey Point.  Introduced to the findings of the previous year he, too, was greatly intrigued.  Ed, a friend Mike Nargatan and Noel (a young Filipino who must have had about a 25-inch waste line) went to the Monkey Point area together.  At what had by now become known to us as the ''back door'' in our minds, a rope was tied to a tree growing in the caved in entry area.  The three fellows went down into the tunnel.  The hole was large enough for them to get through but too small for the writer to attempt so he stayed on top in case they ran into trouble.  After about a half hour the rope, finally, began to wiggle indicating someone was coming up.  A call down the hole ''who is coming?'' brought no answer.  Surprisingly, a head appeared and a young man climbed out.  He was one of four young men from the Faith Academy in Manila.  In 1989 the writer had shown him, and a group of other young men, around the Island but had not seen them since.  The Faith Academy is a school for offspring of parents who are missionaries in the South Western Pacific area.  These young men had climbed down roots  growing along the side of the void around the air shaft.

Later  during  the stay on Corregidor, Ed and the writer collaborated with Captain Daniel Howell, USMC, retired, who lived in a small home he had built in James Ravine.  Danny had three Filipinos working for him.  He volunteered to have his men enlarge the hole into the tunnel so we could more easily get through.   This they did  and we could all now get into the tunnel.  Some video footage was made of the inside the tunnel and some measurements and compass readings taken.

When first entering the hole, a long, very steep slope leads down at about a 45 degree angle.  A rope is  very helpful in the decent because there are several drop-offs of four or five feet.  At the bottom of the slope the tunnel levels off and there is a good deal of room.  Offhand, it appeared the tunnel walls must be at least 12 feet wide  and, perhaps, even higher.  The walls and ceiling are raw rock and dirt although there are signs they, at one time, had a concrete lining.  This lining, however, has, mostly, been destroyed.  At the place where the tunnel levels off there are two side laterals.  The one to the left, or Northeast, is the longest.  Crawling under the concrete tunnel lining, which has been  badly blasted, one can go  back about 38 feet from the main lateral.  At the rear of this side lateral many objects shaped somewhat like grenades are strewn around the floor.  They are about 3 inches in diameter and 4 or 5 inches long.  It is difficult to determine what material they were made of.  They are crumbly like they might be rusted iron but the color is darker than rust. almost like carbon.  Whether these objects were left over from Station ''C'' days or whether they were Japanese is hard to determine.  Danny guessed these might have been fuses of some sort and that could very well be correct.  The side lateral on the right, or Southwest is much shorter than the other, measuring 12 feet.  There is little detail in the short lateral from which to determine its possible use.  Perhaps it was the office of the Naval commander of the station.  The larger lateral had been used to house the “Purple Machine”.

Continuing straight ahead (to the Southeast), the tunnel leads to a cross tunnel.  To the right (Southwest) about 50 feet is the opening, or void, around the air shaft.  Here it is light and airy.  The thought, however, comes to mind:  ''people toss stones down from above to see how deep the hole is--what if someone else finds the opening on the surface and decided to see how deep it is?''  It did not seem to make much sense to stay in the open very long.  Moving on to the Southwest a short distance, the tunnel, reaches a point where there is only room enough to crawl.  After about 33 feet from the shaft the tunnel is completely blocked all the way to the ceiling.  This point appears to be under the road to Kindley Field.

There is a lot of debris throughout the tunnel and the floor is very irregular, almost wavy.  There are places where debris is piled high and other places where it must be close to the original floor level.  This debris probably came from a combination of the big blast in 1945 and many years of the ceiling sloughing off loose material.  It is possible Japanese, digging for the bones of their comrades, may have thrown spoil up into piles sometimes nearly reaching the ceiling, although there is no evidence of the Japanese exploring the tunnel ruins.  That raises a question:  was the tunnel blocked as a result of the explosion in 1945 or was it thrown up by digging Japanese?  Even with piles of rubble, the ceiling is high enough in most places to stand up.  Some of the walls of the tunnel are lined with reinforced concrete but most of the lining appears to have been blasted loose by the explosion in 1945.






The exception is, when, instead of turning to the right at the end of the lateral, one takes a turn to the left and heads Northeast.  Here there are several places where a person has to crawl.  Eventually, following the tunnel becomes an exercise in “slithering”.  After awhile the floor begins to climb rapidly, much the same as in the slope where we entered.

Following this lead, slithering and climbing for quite a distance with surprisingly  good air the tunnel eventually comes up to near the surface at the facilities noted near the Panama Mount.  It had became evident there had to be another opening  nearby since, at times, there was actually a stiff breeze blowing past which raised a powdery dust.  Finally a point is reached  where the tunnel is blocked.  But off to the side daylight shows. In fact sunlight actually shows through a hole, perhaps, a foot in diameter.  That was much too small to climb through.  Returning to the intersection between the tunnels, measurements of  the distance between the hole and the intersection at appeared to be about 90 feet apart.  These measurements cannot be precise because of the uneven ground and the question of, exactly, where to measure from and to.

Returning to the surface,  compass bearings were taken at the same azimuth observed in the tunnel below.  Following this bearing on the surface for the distance between the shaft and the small hole where sunlight  had been seen, one arrives at the ruins of the facility which, originally, was thought might be a store for the Panama Mount.

Once the layout of the tunnel complex  began to become to come clear, other details began to emerge.  Two iron pipes had been observed while down in the  tunnel.  They lead from a short distance above the tunnel floor and into the top of the tunnel.  At the time they were only interesting observations.  Later, in discussions with  Captain  Whitlock , it was learned one of the pipes was an exhaust  for a diesel electric power generator.  The other handled the exhaust from air conditioning equipment.

All the observations on the surface and in the underground portion of the facilities began to make the layout  clear.  The entrance, previously  thought to be the rear exit was, in reality, an entrance to the main lateral, leading to the North East from the main tunnel.  The new hole found at the Northern end of the main tunnel was connected with the “Exit, 100 steps” shown in the stylized sketch.  Beyond the blocked spot to the South of the air shaft  was the part of the tunnel which was destroyed by the explosion in 1945. 




Many years have passed since that cataclysmic day when the Navy Intercept Tunnel blew up.  Now visitors can walk around the area without fear of the earth shaking and rocks, dirt and other debris being blasted all over Monkey Point.

During all those years survivors and others interested in the story of the Navy Intercept Tunnel have accepted the concept the facility was completely destroyed by the blast.  This study shows that supposition to be wrong.  The Navy Intercept Tunnel was not completely destroyed by the blast!  It was badly damaged, that is certain.  But a good deal of the complex still remains in a recognizable condition.

Although no physical indication was found of other visitors having entered open parts of the Tunnel, it is believed the people mentioned in this study were the first to enter the tunnel and fully understand what they were seeing.


Wreckage of the Sherman Tank known as "Murder Inc."

Wreckage of Murder Inc at Monkey Pt.

Author: Don Abbott
Layout: Carl White










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Photograph of Explosion at Monkey Point courtesy Daniel MacRaild