Due to friendly fire, shells are falling around the unit. They are forced to leave and find refuge in a cave. It becomes obvious that Hawkeye can't go more than a few feet into the cave. What transpires after we see evidence of his incredible fear, is a series of events leading to a return to the camp in order to assist a patient. There is one of those scenes at the beginning where Potter talks to a smug bureaucratic Major who tells him that there are no bombs falling in their sector. A patient named O'Malley is in grave danger if he isn't near a medical facility. Potter needs to have everyone on board but it does present problems. If you've ever suffered from this malady, it can be devastating.