Sergeant Major Zack Carey (James Garner) arrives at his last duty post, an Army base in Georgia called Fort Clemons, with his wife Ladonna (Shirley Jones) and his son Billy (C. Thomas Howell). The guard at the main gate welcomes him as he enters with his family in a station wagon. Behind him is a moving van with their belongings and a World War II Sherman tank on a trailer (he tells the guard he never said he travelled light). Personnel help him remove the tarps from his prized possession as Ladonna supervises the moving of furnishings into their on-base housing. As Zack rolls the tank onto solid ground, a staff sergeant reporter from Soldier Magazine named Jerry Elliott (Mark Herrier) interviews him, as he is the only Army man who owns a tank. He has restored it over fifteen years, adding a radio and PA system so he can drive it in parades and other events. Of his two sons, his eldest son Jonathan has died and Billy, born six years later, is just 16. When asked why anybody would want to own a tank, he replies that it is very hard to shoot yourself while cleaning it.Zack visits the base commander, Major General V.E. Hubik (Sandy Ward), who is familiar with him, welcomes him wholeheartedly and takes him on a tour of the base. Zack has made an offer on a fishing boat on which he and his wife can enjoy retirement. The General says Zack could be the next senior Sergeant Major of the Army and work out of the Pentagon, but Zack says he has only one son left who will go on his own soon, and he doesn't want to miss any quality time with him. Back at the house Elliott the reporter asks Billy what his father is like, and Billy says he is a cross between George Patton and Danny Thomas.Ladonna recommends that Zack goes to the local NCO club and he finds its more like a disco, geared to a younger crowd and much too noisy for his tastes. He does run into an old friend, Ed Tippett (Dorian Harewood) who works at the base Provost Marshall's office. When Ed says to come meet the wife, Zack says he knows Linda and Ed corrects him: Gwen is the new wife. At home Zack is slightly disheartened and talks to Ladonna about the club and his friend's divorce, saying all he wants to do is finish his duty and get on the boat, then the couple share a cuddle.At his first assembly with his command personnel the next morning, Zack stresses taking care of their own without problems reaching their superiors, and keeping to Army regulations in all matters. He also says he wants to see a proper bar on the base so Army personnel of a certain age don't have to dance, as he calls it, the funky monkey. Early the next morning Zack hits the battalion field to do his morning jog and shouts for all to hear that he finds himself alone; in moments the entire battalion has filed out of their barracks and they form ranks on the field to engage in early morning physical training with their sergeant major. The General is awakened by the sound of the troops passing. He watches Zack out his bedroom window and smiles.Sometime later, when Ladonna gets home, Zack happily announces that the sellers accepted their offer on the boat. He forgot she is entertaining the NCO wives in the house that night, so they can't eat dinner at home or celebrate yet. She suggests Zack go into town for dinner. He stops at the local bar, the Outpost Café, and talks with a woman named Sarah (Jenilee Harrison), who has aspirations to go to California and become a beautician. Zack becomes loose with the beer, says he has been in the Army for 30 years and jokes that he should go into the Navy now that he is a boat owner. He starts singing a loud shanty which interrupts a pool game being played by Deputy Euclid Baker (James Cromwell) and some of his friends. Euclid quickly makes it obvious to Zack that the Army isn't particularly welcome. He then tells Sarah she has wasted too much time on Zack and should be turning tricks with paying customers, then he slaps her. Zack says that the display was not necessary, but Euclid takes another swing at Sarah. Zack punches and roughs up Euclid, then gets hold of the deputy's service pistol; the bar patrons step back in alarm, but he simply drops it in the fish tank on the bar and leaves. Sarah yells at him that she could have lost her job, but he says a simple thank you would have sufficed. He immediately goes to Ed's house to tell him what happened, knowing he has made a mistake which will bring the local constabulary looking for him. Ed says the sheriff is a particularly mean variety of Georgian cracker, and it might take considerable money to get out of the situation.The next morning Euclid greets the sheriff, Cyrus Buelton (G. D. Spradlin) and brings his morning cup of coffee. Buelton upbraids Euclid for getting beaten up by somebody and not putting that person in jail. A mark on the deputy is a mark on him, and something he won't tolerate.Zack is spotted eating at the enlisted mess hall instead of the NCO mess, ruffling the feathers of Mess Master Sergeant Johnson (John Hancock), to whom it appears to be an unannounced inspection and a breach of etiquette. He storms over to Zack in a huff, but Zack explains he chose to come in because the food smelled good. He praises the clean facility, the quality of the food and that nobody slopped food onto the plates, all of which Johnson says is no less than he expects of his staff. When Zack gives high praise to the mess sergeant's own apple cobbler, the man softens and Zack earns his respect.Buelton and Euclid visit Sarah in her trailer. The sheriff awakens her and asks if she believes in Wonder Woman or the Lone Ranger. When she seems confused, he talks to her about thinking that Zack and Army men like him are her heroes. He demands that she roll over and drop her pants so he can enforce the lesson with his belt that there is no Lone Ranger. She complies. When he sees Euclid looking down at her and smirking, he whacks him upside the head before proceeding with Sarah's whipping, which she silently and tearlessly endures. The sheriff then visits the Provost Marshall's office. Ed has expected his arrival and excuses the white clerk at the counter to take on the visitor himself. Buelton says he wants Zack in his own jail and demands he be handed over. Ed casually says he will have him delivered at once, but doesn't move. Buelton challenges Ed and calls him Sambo. Ed says he will also order that by five o'clock the town be off limits to all military personnel to prevent more problems, knowing it would affect the town's livelihood. Ed then warns the sheriff, calling him Jim (as in Crow), not to exceed the speed limit leaving the base or risk spending time in his jail. Insulted, Buelton returns to his office and demands Euclid get every piece of information available on Zack.At a visit to the post hospital Zack sees a crying five-year-old boy being held down by his mother while a doctor stitches cuts to his bloodied face. The mother says his daddy isn't mad at him anymore, and Zack realizes what has happened. He calls the kid's Army father, Corporal Harris (Larry Jordan), into his office and asks if he hit his son. The man becomes defensive and says it is none of his business, but Zack makes it his business, offering to spar with him at the base gym if he feels the need to vent anger, and demands he get counseling. Harris continues to be stubborn, so Zack puts him against the wall and warns that he will visit the hospital daily to make sure the man doesn't lay another hand on the boy, threatening to risk his rank, retirement and the stockade if necessary to stop him, and the chastened man is dismissed.Zack and Billy talk about the boat at home, and Billy mentions naming it the Johnny Boy, saying it would be fitting since Johnny was his favorite son. Zack sets him straight, saying he and his mother had a different and unique relationship with Johnny, who always tried to prove himself (which might have been what had gotten him killed). Billy should never feel that Ladonna or he loved either of them more or less than the other. At school Billy is summoned to his locker. Euclid and Sherriff Buelton ask him to open his locker, but he finds a different lock on it and his combination doesn't work. On orders, the maintenance man breaks off the lock, and a bag of marijuana has been planted inside. Zack contritely visits the jail to see Buelton, and he and Euclid take great joy in humiliating him as he admits his fault and asks what he needs to do to get Billy back. Buelton says that the judge, who happens to be his brother-in-law, will surely send Billy to the county farm for two or three years of hard labor. The sheriff takes Zack on a tour of one of the work farms and has a supervisor pull a black worker off a truck, where he was on break from the work detail, to exercise negative feedback, which consists of beating the man for malingering. Buelton demands $10,000, which he feels Zack can afford after getting word of the article in the magazine. He also warns not to bring in any lawyers. Zack says he will play it his way as long as Billy is safe. He visits his son in jail and tells Billy that Buelton is getting revenge, he will be set free soon and to stay strong. Billy calls his dad sir, and Zack stresses to Billy that he should be as polite to his captors.Back at home Ladonna slaps Zack, furious at him for "whoring" and putting their son in danger. She refuses to listen and says she wants to get a lawyer and bypass any of his ideas. The next day, while Zack is conducting a firearms inspection, Ladonna pulls up in the car and confesses that she had no idea what kind of man Buelton was. At the sheriff's office, Zack quietly hands Buelton the money in a bag, which the sheriff says will keep Billy alive for a while, and Zack argues additional shakedowns had not been part of their deal. The sheriff says hiring the lawyer was dumb. Billy has been tried and sentenced to three years of hard labor at the work farm where, without protection, he might be victimized by degenerates or shot while trying to escape. In the jail cell, Billy has suffered a beating and yells at his father, as he has been told a version of what happened with Sarah at the bar, asking if she was worth it. Zack goes home and thinks things over, weighing his options. At dawn he goes to his tank, prepares the vehicle and then drives it toward the main gate. Major General Hubik is apprised of the situation, and he tells the guards to bar the gate. Zack simply swerves past them, taking down part of the fence as he heads into town.Zack awakens Euclid at the jail with his tank and trains the muzzle on him, asking him to let his son out of jail. Euclid says Billy was taken to the county farm overnight as a precaution, and only a couple of drunks are inside. Sarah has come out of her trailer and says the lawyer they hired is also in the jail. Zack has her retrieve Euclids keys to release the prisoners, then tells him to take the radio out of the squad car. Euclid refuses, saying it's a new radio and the sheriff would kill him if it got ruined, so Zack uses the main gun on the tank to take out the squad car. Then he shoots the main phone line out of town with a machine gun. He drives through the jail using his tank as a juggernaut to level the building. Finally he has Euclid strip naked and Sarah handcuffs him to a telephone pole. She asks Zack to take her with him, as she can't stay there anymore, and he agrees.Outside the work farm, they observe Billy through binoculars, helping a work crew. Zack blasts a truck as a diversion and uses the sound system in the tank to tell Billy to lie down flat; he aligns the tracks vertically on either side of Billy and drives the tank over his son to retrieve him using the hatch in the floor, and the trio take off. The police are called in to block the road, but Zack drives the tank over the squad cars. Buelton talks to the governor of Georgia (Wallace Wilkinson) saying he has a 52-year-old sergeant major who is crazy, along with a sixteen-year-old "dope fiend" and a 20-year-old hooker in a Sherman tank, and asks for help, but he refers the sheriff to the Army.Billy helps Zack with tank maintenance while Sarah washes in the river. He has a disagreement with his father because of Sarah's presence, but Zack says she is willing to testify how she was arrested for vagrancy and forced into prostitution by Buelton on a trumped-up charge, lending weight to their cause, and Zack can then add his testimony as well. He tells Billy they're not running from, but to, the law, hoping to go over the state line, where true authority in neighboring Tennessee can put a stop to Buelton's abuse of power.Buelton visits Hubik to demand aid from the military. Hubik replies the only indiscretion the Army has against Zack is his destruction of a 20-foot section of fence, and Zack had resigned earlier in the day. Then he mentions the Posse Comitatus Act, a law prohibiting the Army rendering aid in a civilian matter without the permission of their Commander in Chief: the President of the United States. The sheriff, unfamiliar with the term, misinterprets it and takes umbrage, thinking he has been called a "pussy communist," and storms off to deal with Zack in his own way.The news media has received word of the fugitives in the tank. Buelton puts his men at every gas station to the state line to stop Zach from refueling. When the tank begins to run out of gas, they pull up to some gas pumps at an off-road home. When Zack restrains the owner, he is surprised when Mr. Gant (Danny Nelson) doesn't protest. He says Zack can have anything he wants, as his sister's son was sent to the work farm and never got out. After a quick rest and a meal, they continue on their way. Buelton speaks to his supporters about Gant abetting a felon. Folks appear at the property with torches to burn the home down and have him serve as a lesson to others. He stands up to them, and suddenly the tank appears. Zack has doubled back to help Gant and drives the mob off.As they take on supplies from Mr. Gant, Billy works with Sarah. He has been cool toward her until finally she sets him straight. Zack only wanted to talk, she says, and if he had taken her back to the trailer to cheat on Ladonna, as most men shes known has, the events would have played out differently. Billy realizes Zack did nothing wrong and gains a new understanding of his father. Meanwhile Gant helps Zack plan his trip to the Tennessee border, suggesting a rougher route which will take them away from a bog where Buelton suspects he may be headed.The tank slips a track as they detour through some rough country, and Zack and Billy work on it together. Billy mans the tank to move it forward when his dad gives the word to Sarah, but Zack mumbles to himself while readying the tank to reset the track, Sarah mishears him as giving the okay and signals Billy to move the tank. The tank jerks and Zack takes a blow from a crowbar to the torso, causing immediate pain. He says his ribs are broken, and later he starts coughing up blood. It becomes apparent that he has internal bleeding, and they need to reach the state line and help soon. Billy says he can handle the tank, as he helped build it. When Zack protests that Billy doesnt have to prove anything like Johnny used to, Billy says he is not like his brother, but more practical like his mother. He realizes his dad took the blame for something that was not his fault. Billy decides to go flat out toward the border rather than moving only by night, to get them out of danger faster.Ladonna talks to Billy and Zack via the military radio and apologizes to her husband for what she said to him. Then she goes to the governor of Tennessee for help, but at first he refuses to see her. She talks to the television news reporter, asking the wives watching to call the governor if they support her cause and ask that he give her five minutes of his time. A helicopter carrying a newsman hovers over the tank while broadcasting on live television, and he interviews Billy through the tanks radio. Billy tells the people that he loves and respects his dad and has no intention of giving Zack over to Buelton. Watching the show is a gang of bikers at a bar who admire Billy and his old man.With the public's outcry, the governor finally gives in and talks to Ladonna in his office. If Zack can cross the state line, she wants the governors promise that a fair trial can be held there instead of in Buelton's jurisdiction. The governor has issues because one of the fugitives is an alleged prostitute, and Ladonna says that it is her own husband and son with the alleged 20-year-old prostitute, and he should have no problem with the matter if she doesn't. She then mentions that she has reporters and his own voters outside waiting for her to deliver his answer, suggesting that he should consider if he will be perceived as a man who wants to see justice done, or as an asshole. He asks if she is threatening him with blackmail, and she brazenly says she is. He agrees to help Zack if the tank arrives, promising in a television interview that there will be a hearing in his state before any extradition is considered.Buelton gets his own supporters together to force the tank, with the aid of roadblocks, to detour into a recessed open field by the side of the only road leading to the state line. The plan is to stall the tank there with mud, and water tanker trucks begin hosing down the dirt in the field as the semis to block the highway are put in place. He has a man named Avery (Don Young) set up a bazooka to fire rounds at the tank when it arrives to ensure it is disabled. At the crossroad on the other side of the border, hundreds of Zack's supporters, who have watched the story play out on television, come to help in any way they can, along with television crews and helicopters. The bikers have also set up to await their arrival. Ladonna gets on the radio to the tank and tells her family and Sarah that they have won.Buelton and his crew hide at the edge of the road with their guns. As the tank approaches the border and he sees the way blocked, Billy steers the tank off the road as expected and starts across the muddy field. Avery fires the bazooka but misses, since he hasn't used the weapon since his own military days, but his second shot hits the tank, and it shuts down. Buelton announces that they can all wait while the climbing temperatures take their toll on the tank's occupants. The general arrives by military helicopter to join Ladonna. When he says the tank has slipped a track and will only move if it is pulled out, the bikers confer on what to do, then they start to unload supplies off a parked truck. When the driver asks what they're doing, they openly reply, "Stealing," to no objection; everybody pitches in to build what turns out to be a ramp. Billy finally goes over the PA to ask about how his father will be treated if they surrender, as Zack is feeling worse due to his injuries. Buelton gives his word that Zack will go to the hospital immediately. Then a biker rides out on the completed ramp, sailing through the air on his motorcycle carrying a rope to be attached to a tow cable that can help pull the tank out of the mud. Billy exits the tank from the bottom hatch and helps attach the cable while Sarah holds Buelton's gunmen at bay with the machine gun.Everybody, with Hubik and the Tennessee Governor on hand, begins to pull on the cable. Buelton tries to instruct his aides to shoot into the crowd, but the armed troopers on the Tennessee side take aim and warn that there will be another Little Big Horn if they do that, so they run into the field and pull from the rear of the tank, which isn't budging. Buelton jumps onto the tank to demand Zack come out, but Sarah turns the turret to knock the sheriff to the ground. The crowd spots a bulldozer that can handle the cable. It is put into use, and along with pulling supporters against the meager crew on Buelton's side, the tank is slowly pulled up the incline, over the Georgia state line and into Tennessee. The sheriff and Euclid are left in the mud. Ladonna embraces Zack and Billy as they exit the tank, and Billy kisses Sarah as the crowd cheers.