Past Time And Cold War

"Wildcat."

How do we know when the characters are? This is disclosed gradually:

"'Your precious union is a hundred million years in the future...'" (p. 42)

"...the Jurassic mist." (ibid.)

"...along the gulf that would some day be Oklahoma." (p. 44)

"'The international situation is critical. You ought to be thankful you are safely back in the past." (ibid.)

"'...not a woman for a hundred million years...'" (ibid.)

The bureaucrat, Symonds, lectures the men, and thus also the readers, on the limitations of time travel in this one-off scenario.

In the twentieth century, the Russians:

probably know that the US has time travel;

but will have threatened an all-out attack if war material is sent into the past in any quantity;

have a satellite base;

have "'...agreed to make the moon a neutral zone.'" (p. 46)

Thus, the international situation in the twentieth century affects these men who are drilling for oil in the Jurassic but who expect to return home.