In November 1944, Chief Bosun's Mate Sam McHale is aghast to learn that he is being transferred from his beloved aircraft carrier to a Navy-operated weather station in the Gobi Desert in Inner Mongolia. Capt. Gates explains to McHale that accurate weather forecasts are crucial to the Allies' success in the Pacific theater, and that his practical experience is required by meteorologist Commander Hobart Wyatt and his crew of scientists: Jenkins, Walter Landers, Wilbur "Coney" Cohen, Elwood Halsey, Frank Swenson and Paul Sabatello. Despite his longing for the ocean, McHale adjusts to life in the desert during the following six months, although Wyatt is bemused by McHale's dependence on the military's strict chain of command. Three weeks before they are to be relieved, the crew learns that Japanese cavalry has been spotted nearby, and McHale begins plans for increasing the outpost's negligible defenses. The group is also baffled by the arrival of a tribe of nomadic Mongols, who camp at the station's oasis. After determining that the Navy men are not interested in the oasis' grass, the Mongols' leader, Kengtu, expresses no further interest in them until Elwood attempts to take photographs of the tribe. The Mongols react hostilely, but McHale gains Kengtu's respect when he shows him how the camera works. Observing the Mongols' riding expertise, former cowboy Jenkins muses that they would make an excellent cavalry. The next day, Kengtu orders his people to return the many things they have stolen from the station, although McHale allows them to keep his own cap and Wyatt's dress uniform. Later that day, the Navy men learn that due to increasing pressure from the enemy, they will not be relieved. Hoping to persuade the Mongols to help them defend the station, McHale requisitions sixty saddles, and although the order is met with bewilderment, the saddles soon arrive and the delighted Mongols begin training with Jenkins, who dubs them the "1st Mongolian Cavalry, U.S. Navy." Before long, however, the camp is bombed by Japanese planes, and Wyatt and several Mongols are killed. The radio is also destroyed, and McHale is disappointed when the Mongols disappear, leaving them alone and defenseless. Rather than walking 300 miles to the nearest weather station, which might also have been attacked, McHale decides that the men should travel 800 miles to the sea. The men are flabbergasted, but McHale's determination to return to the ocean prevails and they begin walking. Hoping to reach Peking, and from there sail to Okinawa, which is held by American forces, McHale drives the men onward, and they stop at an oasis at which some Chinese traders are camped. Also at the oasis are Kengtu and his people, and McHale reproaches the chief for deserting them. Kengtu replies that he had to protect his people from the "birds in the sky," and when McHale demands protection in exchange for the saddles, Kengtu returns the saddles. Chinese trader Yin Tang then offers to give McHale four camels for the saddles, and the next day, the Americans travel with the Chinese. That night, however, the treacherous Yin Tang attempts to kill them, but is stopped by the arrival of Kengtu and his men. Kengtu tells McHale that his people want the saddles back and are willing to escort the Americans to Peking, provided that they dress in native garb to avoid the Japanese. McHale agrees, although the men worry that they will be considered spies if they are captured because they will be out of uniform. Kengtu's plan appears to be working, however, until they reach the Chinese village of Sangchien, which is a garrison for the Japanese. Power-hungry Mongol Tomec, fed up with the troublesome Americans, appears to persuade Kengtu to turn them in, and later, McHale is horrified when Kengtu leads them into an ambush by Japanese soldiers. The Navy men are taken to a prison camp near the ocean, and when he is questioned by a Japanese officer, McHale refuses to divulge any information about the remaining weather stations. Angered, the officer holds the men as spies rather than prisoners of war, which means they will be shot. Their depression is lifted, however, by the arrival of one of Kengtu's men, Wali-Akhun, who was arrested while wearing Wyatt's stolen uniform. Wali reveals that Kengtu has arranged for their escape, and that night, they sneak out of the camp and to the docks, where Kengtu is waiting with a Chinese junk. Kengtu explains to McHale that he did not betray them, but rather tricked the Japanese soldiers into transporting them to the ocean. An alarm sounds, and as a Japanese search party approaches, Kengtu and his men are forced to board the junk and accompany the Americans. They are pursued by a motorboat, but are able to sink it with an ancient cannon stolen by the Mongols. Coney is killed during the battle, however, and the men soberly set sail for Okinawa. Eleven days later, the junk is spotted by American planes, which are about to bomb it until they see a large sign, with the inscription U.S.S. Cohen painted on it. The men are rescued, and soon after, Kengtu is returned to his people, along with sixty saddle blankets. Kengtu and McHale say farewell, and when McHale tries to explain that he is not the head chief of the Navy, as Kengtu had mistakenly thought, Kengtu replies that it is the Navy's mistake, not his.