Once, before 1990 or.so diesel engines were hard to start cold. You either left them running or plugged them into the wall so the heater instead could keep them warm. It wasn't unusual to leave a truck running all day because otherwise it wouldn't start in winter. In Russia they often built bon fires under their trucks in the morning. I know of tractors that have a gas engine just to start them, which also worked, the gas engine would run at full speed for a few minutes until the engine would finally run.

Not that the above is historical. Modern batteries are much better. Direct injection engines start almost as fast as gas engines these days.