Three Successive Timelines II

Poul Anderson, The Shield Of Time (New York, 1991).

The three timelines were:

(i) Lorenzo does not make a flank attack.
(ii) Lorenzo makes a flank attack and wins the battle.
(iii) Lorenzo makes a flank attack but is stunned by Everard.

(i) and (iii) have the same historical outcome but (iii) is more complicated. It reaches the same destination but by a longer route.

It is idle to ask, "What would Everard have been doing in 1137 if it had not been necessary to sabotage (ii)?" This amounts to asking, "What was Everard doing in 1137 in (i)?" The answer is that he was not there/then.

By noting what Everard did in timeline (iii), we can infer what he would have done in timeline (i).

(iii)
In 18,244 BC, Everard is on holiday at the Pleistocene lodge where he is informed of a temporal catastrophe in twelfth century Italy.
Everard intervenes in twelfth century Italy until the crisis is resolved.
He returns to 1990 and starts a holiday with Wanda Tamberly.
In San Francisco, on 8 March 1990, his holiday is interrupted when he is asked and agrees to intervene in Paris in 1307.

(i)
In 18,244 BC, Everard is on holiday at the Pleistocene lodge.
He returns to 1990.
In New York, on 8 March 1990, he is asked and agrees to intervene in Paris in 1307.

Since he lives an indefinitely extended lifespan, it does not matter that he does more in (iii) than he did in (i). Thus, crises like (ii) do not prevent him from doing anything that he would have done. They merely increase his workload.