in WW1 when US Marines first went into combat in France they were issued hardtack. On the box the date 1865 was noted. Apparently, while hard as a rock it was neither bug infested not rotten. I don't think the Marines really appreciated the gesture but at least they were rations.
In WW2 on Baatan the Japanese captured several 3" Ordinance rifles that had been converted to breach loading
arty... they were put into use by the Japanese and used against US troops when they retook the island.
WW2 again, German POWs in the Carolinas were issued
CS shell jackets made in NC during the CW. This created at least one amusing moment when one German, in a passable southern accent, asked a NC officer if he happened to know the address of Ms. Scarlett O'Hara.
Another thing that makes you wonder I suppose.