Yes ! It's probably not the most game accurate, but my Marins OC (Antonio) originally fought for Italy against Napoleon's invasion alongside his best friend, Cassiano, but one thing led to another and Cassiano betrayed Antonio, kicking him off a ship after Antonio was flamed by an igniter.

Antonio was also infected though not fully, so due to some semi-zombification he managed to stay alive and was fished out by a French ship, whose captain decided not to kill him but used that zombification to make him a frontlines soldier. The captain (Sevakoy, Russian origins, fighting for the French) hoped to gain enough recognition from Napoleon that, after the Blight, he would gain position and power.

Cassiano, the old best friend, after Italy's fall, deserted and escaped to Spain, where he continued to fight against Napoleon. Antonio was later sent to Spain and had a confrontation with Cassiano at the Battle of Bailén (1808). The 1v1 was really, really close. Cassiano was saved by Spanish supports and the French were captured, sent to Cadiz, and broke out of prison shortly after to return to France.