Turning Points

Poul Anderson's "Star Of The Sea" has two turning points:

Janne Floris, swooping down on her timecycle, kills Roman sailors raping Edh;

Heidhin commits suicide as the only way to release himself from his oath to fight the Romans as long as he lives.

Between these two moments, is the potential for a divergent timeline:

if Floris had not killed the sailors, then they would probably have killed Edh;

if Heidhin had not killed himself, then Edh would have withdrawn into the wilderness, continued to preach war against Rome and founded a new religion.

By investigating a problem, the Time Patrol agents caused the problem but then resolved it. And, because of their intervention, Edh, instead of dying young, lives into old age as the messenger of a peaceful goddess, reinforcing Christian incorporation of Pagan imagery and thus strengthening the Time Patrol's timeline.

In this short novel, Poul Anderson:

informs and educates his readers about the Northern revolt against the Roman Empire;
presents convincing historical fiction about Veleda, Buhrmund, Petillius Cerialis and others;
dramatizes the development of religion;
contrasts a first century wilderness with modern Amsterdam;
creates a subtle time travel paradox.

Later:

"'Cerialis became governor of Britain, where he conquered the Brigantes.'" (Time Patrol, p. 632)

I attended some neo-Pagan gatherings called "Briganti Moot."