Filmed at Fort Benning in Columbus, Georgia.
The Sherman tank seen in the film came from the Ropkey Armor Museum in Crawfordsville, Indiana, USA and is owned by Dave Ropkey - both Ropkey and the museum are billed in the final credits.
The Posse Comitatus Act mentioned in the movie is a real life American statute first assented in 1878. The act was passed to stop local, state and civil authorities from utilizing the military for law enforcement. It doesn't stop this from happening, but the authority to do so must come from the United States Constitution or Act of Congress, and usually comes from the direction of the president.
The type of army tank that US Army Command Sergeant Major Zack Carey (James Garner') owned was a World War II era Sherman Tank, aka an M4 Sherman Tank. Previously known as the M4 Medium Tank, the tank is a medium tank, and was named after Union General William Tecumseh Sherman. Around 50,000 of them were manufactured, most of them around World War II. The tank was designed in 1940 and first produced in 1941.
Actors James Garner and James Cromwell would later co-star in Clint Eastwood's Cowboys do Espaço (2000) around sixteen years later. In that film, Cromwell was Garner's superior. James Cromwell also appeared on an episode of the Rockford Files.