Sentence 1: In 1868 the Satsuma and Choshu clans, never a real threat to Tokugawa authority as long as they remained rivals, joined forces to overthrow the shogun and restore the authority of the emperor, the 14-year-old Mitsuhito.

Sentence 2: Satsuma and Choshu clans joined forces in 1868.
Available choices:
A). yes.
B). it is not possible to tell.
C). no.
Is this second sentence entailed by the first sentence?
A).