Time Wars

In Poul Anderson's The Corridors Of Time, the time war is the Warden-Ranger conflict throughout history with each side aiming for military victory in their future which they are prevented from entering by time travel by their successors. 

In Anderson's "Flight to Forever," the Time War is a defeated Terrestrial Directorate army leaping from the twenty-third to the twenty-fourth century and attempting conquest but suffering another defeat.

What Time Wars, created by Poul Anderson, is I am yet to learn.

As ever, Anderson gives us the impression that he covers every angle on any topic.