QUES:
Who is they in the following sentence?

The invaders showed no mercy to the defenders, but they would not surrender anyway.

ANS:
the defenders

QUES:
Who is he in the following sentence?

Medvedev will cede the presidency to Putin because he is less popular.

ANS:
Medvedev

QUES:
Who is they in the following sentence?

Chase Sapphire has a 24 hour service line for card holders so they would be available to help if their customer encounters trouble.

ANS:
Chase Sapphire