This also happened to be during a hiring freeze, so no new contractors, no temp employees, nothing. Current team of half a dozen or so had to drop everything they were doing, switch over to this project and work ~12 hour days six days a week just to deliver a mostly-broken implementation right at the deadline and spend another week and a half at the same schedule fixing bugs and other issues.
It would have been much worse if the timelines were extended, if it was 6 months worth of work to be done in 90 days I think the team probably would have quit. They were mostly contractors so paid hourly, so they got paid for all the work, but that's still a lot of hours for that many weeks in a row.
I have been very lucky not to come across anything like that yet.
The worst death march I was ever on was against a legislative deadline. Oh god, may I never do that again.