Why Did The Pows Escape

Having wasted enormous resources on recapturing Allied prisoners of war (POWs), the Germans move the most determined to a new, high-security prisoner of war camp. The commandant, Luftwaffe Colonel von Luger, tells the senior British officer, Group Capt Ramsey, "There will be no escapes from this camp." Ramsey replies that it is their duty to try to escape. After several failed escape attempts on the first day, the POWs settle into the prison camp.
Gestapo and SS agents bring Squadron Leader Roger Bartlett (RAF) to the camp and deliver him to von Luger. Known as "Big X," Bartlett is the principal organizer of escapes and Gestapo agent Kuhn orders that he be kept under the most restrictive permanent security confinement, which Col. von Luger,
disgusted by the Nazis and the SS, only makes a "note" of, treating the command with complete contempt. As Kuhn leaves, he warns Bartlett that if he escapes again, he will be shot. Bartlett is then placed with the rest of the POWs, rather than the restrictive holding that Gestapo agent Kuhn had demanded.
Locked up with "every escape artist in Germany", Bartlett immediately plans the greatest escape attempted—tunnels for breaking out 250 prisoners. The intent is to "confuse, confound and harass the enemy" to the point that as many troops and resources as possible will be wasted on finding POWs instead of being used on the front line.
Teams are organized to tunnel, make civilian clothing, forge documents, procure contraband materials, and prevent guards from discovering their work.
Flight Lieutenant Hendley, an American in the RAF, is "the scrounger" who finds what the others need, from a camera to clothes and identity cards. Australian Flying Officer Louis Sedgwick, "the manufacturer," makes tools such as picks for digging and bellows for pumping air into the tunnels. Flight Lieutenant Danny Velinski and William "Willie" Dickes are "the tunnel kings" in charge of making the tunnels. Eric Ashley-Pitt of the Royal Navy devises a method of hiding bags in the prisoners' trousers and spread dirt from the tunnels over the camp, under the guards' noses. Forgery is handled by Flight Lieutenant Colin Blythe, who becomes nearly blind from intricate work by candlelight. Hendley takes it upon himself to be Blythe's guide in the
escape.
The prisoners work on three tunnels simultaneously, "Tom," "Dick" and "Harry." Work on Harry and Dick is stopped so that more work can be performed on Tom. The work noise is covered by the prisoner choir led by Flt Lt Cavendish.
USAAF Captain Virgil Hilts, "The Cooler King," irritates guards with frequent escape attempts and irreverent behavior. While in the cooler, he befriends a young RAF Flying Officer named Archibald Ives, and the two strike up a plan to escape; they are caught while attempting it and returned to the cooler. The experience seems to take a toll especially on Ives, who is close to an emotional breakdown from his time in captivity.
While the British POWs enjoy a 4th of July celebration organized by the three Americans, the guards discover tunnel Tom. The mood drops to disappointment and pushes Ives over the edge. He is drawn to the barbed wire that surrounds the camp and, in a final act of desperation, climbs it in view of guards. Hilts runs to stop him but is too late, and Ives is machine-gunned dead near the top of the fence. The prisoners switch their efforts to Harry.
Hilts, aggrieved by the loss of his friend, agrees to change his plan and reconnoiter outside the camp and allow himself to be recaptured. The information he brings back is used to create maps showing the nearest town and railway station.

End of the real "Harry" tunnel (on the other side of the road) showing how it doesn't reach the cover of the trees

Entrance of the tunnel "Harry" showing scale of distance to far end of tunnel
The last part of the tunnel is completed on the night of the escape, but is 20 feet short of woods which are to provide cover.
Danny nearly snaps from claustrophobia and delays those behind him, but is helped by Willie. Seventy-six escape.
After attempts to reach neutral Switzerland, Sweden, and Spain, almost all the POWs are recaptured or killed. Hendley and Blythe steal an airplane to fly over the Swiss border, but the engine fails and they crash-land. Soldiers arrive. Blythe, his eyesight damaged, stands and is shot. Hendley waves and shouts "don't shoot", and is captured as Blythe dies. Cavendish, having hitched a ride in a truck, is captured at a checkpoint, discovering another POW, Haynes, captured in his German soldier disguise.
Bartlett is recognized in a crowded railroad station by Gestapo agent Kuhn. Another escapee, Ashley-Pitt, sacrifices himself when he kills Kuhn with Kuhn's own gun, and soldiers then shoot and kill him. In the commotion, Bartlett and MacDonald slip away but they are caught while boarding a bus after MacDonald blunders by replying in English to a suspicious Gestapo agent who wishes them "Good luck". Hilts steals a motorcycle, is pursued by German soldiers, jumps a barbed wire fence but becomes entangled in another and is captured, he escapes execution as a spy by showing them the airforce label on his
shirt.
Three truckloads of captured POWs go down a country road and split off in three directions. One truck, containing Bartlett, MacDonald, Cavendish, Haynes and others, stops in a field and the POWs are told to get out and "stretch their legs." They are shot dead. In all, fifty escapees are murdered. Hendley and nine others are returned to the camp. Von Luger is relieved of command of the prison camp and is driven away by the SS for failing to prevent the breakout.
Only three make it to safety. Danny and Willie steal a rowboat and proceed downriver to the Baltic coast, where they board a Swedish merchant ship. Sedgwick steals a bicycle, then rides hidden in a freight train boxcar to France, where he is guided by the Resistance to Spain. Hilts is brought back alone to the camp and taken to the cooler. Lieutenant Goff, one of the Americans, gets Hilts's baseball and glove and throws it to him when Hilts and his guards pass by. The guard locks him in his cell and walks away, but momentarily pauses when he hears the familiar sound of Hilts bouncing his baseball against a cell wall. The film ends with this scene, under the caption,