Overwhelmed by adversarial forces or circumstances (either animate or inanimate), so as to be facing likely defeat or to have already been defeated.
Near-synonyms: outgunned, in too deep, out of one's depth, over one's head
The company's executives mistakenly assumed that they could have a 20-person team cover the work of a 40-person team, causing the staff to be wholly outmatched and thus leading to missed quality defects.