In 1983, U.S. Marine Gunnery Sergeant Tom Highway, a veteran of the Korean War, the Dominican Republic campaign in 1965, and three tours in Vietnam, is in jail for drunk and disorderly conduct. In court, the judge reads the charges against him and releases him with a $100 fine, warning that it is his last chance to stay out of prison. Back at his base, Highway is summoned to Major Devin’s office. Devin informs him that he has been transferred to 2nd Recon Battalion, 2nd Marine Division. Later, in a redneck bar on amateur night, Stitch Jones, a black guitar player, is tossed out by a couple of cowboys. He hitchhikes in the rain, and catches a ride with the same bus that carries Highway to his next assignment. Jones sits next to Highway in the only empty seat, and attempts to strike up a conversation, much to Highway’s chagrin. At a roadside café, Jones sits with the Marine for breakfast and continues his streetwise banter. When the next bus arrives, Highway tells Jones to ask the driver to wait while he uses the restroom. Jones offers to pay for their meals, and Highway leaves a $2 tip. With Highway out of sight, Jones pockets the cash, tells the waitress that Highway will pay the bill, and hops on the bus without telling the driver to wait. At his new base, Highway reconnects with his old friend, Sergeant Major J. Choozoo. Highway’s new commanding officer, Major M. A. Powers, tells Highway that he will not tolerate unruly behavior. Aware that Highway is near mandatory retirement age, Powers tells the gunnery sergeant that he is an anachronism, and out of step with the new Marines. When he meets his new squad, Highway finds them to be slovenly and insubordinate, and is surprised to discover that Stitch Jones is also in his unit. Highway recovers the money Jones owes him, and puts the squad on notice that they will have to shape up. That evening, Highway stops in at the Globe and Anchor bar and renews his acquaintance with Little Mary, the proprietor. Mary informs Highway that his ex-wife, Aggie, is now a waitress at the Palace Inn. Afterward, he stops by the Palace, where has an uncomfortable reunion with Aggie and meets her new boyfriend, Roy Jennings. Jones performs onstage and gets into an altercation with several young male patrons, and Roy aggressively intervenes. When Highway suggests that Roy may be overreacting, he threatens the Marine and kicks Jones out of the establishment. The next morning, Highway begins the task of whipping his squad into shape. When Highway later asks Lieutenant Ring if he can work his men “freelance,” the officer mentions there are no special duties on the training schedule and asks if Highway would like him to join in the exercises. Highway suggests that Ring may have more important duties at his desk, and the lieutenant says that he is preparing a paper on strategy and tactics and brags that he was commander of his R.O.T.C. (Reserve Officers Training Corps) unit in college. He asks where Highway went to college, and the sergeant replies, “Heartbreak Ridge,” a scene of battle in the Korean War. As his squad takes its daily jog, Highway shoots an AK-47, sending the young Marines scrambling. He tells them it is the enemy’s weapon of choice and they need to get used to the sound. Sometime later, Highway waits outside the Palace Inn at closing time reading the latest issue of Elle, a women’s magazine, and watches from a distance as Aggie and Roy go home. When Highway calls on his squad the next morning, they refuse to take his orders and summon “Swede” Johanson, a large and muscular man, to beat up the sergeant. “Swede” takes the first swing, but is quickly subdued by Highway, and the insubordinate Marines fall into line. Later, Ring sends his reconnaissance platoon out on a training exercise, dropping heavy hints that his men are supposed to lose to the “superior” fighting force of Powers. However, Highway ignores the “suggestion,” and has his men attack Powers’s platoon at a location different from the agreed ambush point, completely overpowering the opposing force. Powers challenges Ring and Highway, but Ring stands up for Highway by telling Powers that he gave the Sergeant permission to “freelance” his men. Later, Highway visits Aggie to talk about old times and the fact that his career is coming to a close. He ponders the future and asks what went wrong with their relationship. Although initially receptive, Aggie throws him out of the house when he begins to make physical advances. Highway lands in jail for drunkenness, and Aggie pays his bail. She hints that they may yet have a future, but scolds him for 1968, when he was in Vietnam and she was left to wait at home, not knowing whether he was dead or alive. During another training exercise, Highway’s reconnaissance platoon and Ring’s 1st platoon reach their waterhole objective at the same time. Ring declares his platoon the winner, but Highway objects and, acting as referee, Choozoo orders the men from both sides to wrestle in the waterhole for the prize of being declared winner. Stitch Jones is the last of Highway’s men in the pond, and when two 1st platoon men attempt to drag him out onto the bank, he grabs them in the crotch. They let go, and Stitch forces them out of the water. Stitch and Highway declare victory for the 2nd Recon Battalion, but Ring again claims the prize and orders Choozoo to declare 1st platoon the winner. Instead, Choozoo calls for platoon sergeants Webster and Highway to fight, but Ring asserts his rank and takes on Highway himself. As the Recon men celebrate their victory back at their barracks, Webster informs them that Ring has ordered them to file statements declaring that Highway used unauthorized weapons on the training exercise. The men refuse. Sometime later, at a party given by base commander Colonel Meyers, Aggie and Highway dance and continue their conversation. When Highway suggests that he might buy the avocado ranch he and Aggie used to talk about, she informs him that Roy has asked her to marry him. Highway asks how she responded, but before she can answer, Colonel Meyers interrupts the party with an announcement that the 22nd Marine Amphibious unit’s alert status has been upgraded and all enlisted men and officers are to return to their units. Aboard an aircraft carrier in the Caribbean, Highway and his platoon are deployed to support the U.S. invasion of the island nation of Grenada. As they make their way toward St. George’s University to rescue several stranded American citizens, Highway and his men are ambushed by a small contingent of Cuban soldiers. While his men provide cover fire, Highway flanks the attackers and kills them. As they attempt to cross a bridge, Highway’s men again come under fire, but they overwhelm their opposition and rescue the Americans. Afterward, Powers shows up to take pictures of the victory scene, but Choozoo receives a call from battalion headquarters telling Highway and his men to scout a nearby hill. Powers tells Highway to stay in contact and not to take the hill on his own. As his patrol makes its way up the slope, Highway’s men are attacked by Cuban infantry flanked by Russian armored vehicles. In an abandoned building, Ring finds a telephone and, calls in their position for an air strike. In the ensuing action, Highway’s unit takes the hill, but Powers arrives and berates Highway for disobeying orders. However, Ring again takes responsibility and tells Powers that Highway was acting on his orders. When Meyers arrives, he commends Highway and his men, and busts Powers back to “supply” where he began his Marine career before becoming an infantry officer. When Highway and his men return to the U.S., Stitch tells Highway he is a better Marine than a singer and intends to stay in the service. Highway reunites with Aggie, and together they walk away from the crowd.