Transtemporal
conflict described in a series of short stories and novellas by
Fritz Leiber. Two shadowy
alien races, commonly referred to as the
Spiders and the
Snakes, are embroiled in a
war for supremacy in which the battleground is
history itself. They recruit humans as their
agents, cutting them loose from their lifelines the moment before their
death, and send them through
Time to change history in a way that gives their side the advantage.It's a tough job since history is resistant to change - if, for example, you were to kill Hitler someone exactly like him would simply take his place and do exactly the same things.
The stories rarely focus on the battles themselves, and are instead usually set in the Places, rest and recuperation centers for wounded and battle-fatigued soldiers outside the timestream.