Major Kiefer's anguished memories are of Operation Tiger, a tragic live-fire invasion rehearsal that took place in April of 1944. This took place at the Slapton Sands beach in southwest England. It was a live-fire rehearsal, with the landing craft being launched far enough out for the soldiers to experience seasickness, compounded by the confusion, explosions, noise, and smells of a realistic invasion, as well as encountering the fresh destruction of the beach terrain and the mayhem associated with life fire.
Things went wrong when a German E-boat (PT boat) patrol fleet, attracted by the radio chatter, launched a torpedo attack against the ships and landing boats (LSTs). In response, the fleet was ordered to scatter, which left hundreds of men in the water, resulting in the deaths of over 700 American soldiers and sailors, most of whom drowned. To compound the tragedy, the British did not cease artillery fire once the survivors reached the beach, raining live rounds on the "invaders", which resulted in another 300 deaths; Americans killed by the British.
All of this was compounded by the enforcement of orders to completely conceal what had happened - orders that were necessary in order to preserve morale for the actual invasion. Kiefer's anger at the British was largely due to the loss of these 300 men, the personal trauma he had experienced during and after the exercise, compounded by the gag order.