Apologies if there's a thread for this, I couldn't find one quickly.
I was sticking in a losing game* so I'd get my unit production for defense, and I can usually take my turns quickly. I started a turn though and about half my units in most of my cities were gone, without any (relevant) battles recorded in the battle history. I should have had more than enough gold to cover upkeep, but is unit upkeep subtracted before you get city income? That's all I can think of that could have happened, but it seems pretty stupid. If so though, I should have actually resigned several turns earlier to optimize defense against the guys grabbing my territory.
*game id 2762, Middle Earth vers 5 map.