Top Gunner -- or Jackal as it's known in every other incarnation but the North American arcade one -- is an overhead game set in a warzone. Rescue the good guy hostages in your jeep while annihilating the enemy forces (also in your jeep.)
Stored at 0x0BE60 in the master CPU:
KONANI 1986 8 04 KOJI HIROSHITA MASATO OHSAWA HIROMICHI OKASAKI HIDEYUKI TSUJIMOTO SHINJI TASAKA KENGO NAKAMURA MASAMI TABATA KIYOKO MIZUTANI YOUSUKE UNO MITSUHIRA IDAKA
While the setting of Jackal is intentionally vague, Top Gunner, thanks to a set of graphical changes, is definitely meant to take place during the Vietnam War.
The flag on the player's Jeep is a nondescript orange and blue flag in every other version but Top Gunner, where it's an American flag.
Red flags (presumably the North Vietnam flag) were added to the enemy gates and campsites in Top Gunner.
Strangely, in every version of the game, the final area and the game's progress map have the same red flags.
Five-pointed red stars were added to most of the enemy vehicles in Top Gunner, to really reinforce the whole North Vietnam thing. The only exception to this is the Molotov Cocktail-throwing van.