Overwatch stratagem

[arcane42]

Hi. New to the other side game and have been  reading some of the stratagems. Can anyone tell me how the overwatch one works?

Does each fire team get to take an action or just one? If each one gets to take an action does it only take on team to fail a test for the card not to be put back in your hand?. 

Any help would be appreciated. Many thanks. 

[retnab]

"When you play this Stratagem, choose a friendly unit.  It may take an Action targeting the last enemy unit to Activate this Turn."

It's "an Action", so it's only the one.

[arcane42]

Thought this was the case as seemed overpowered if it was every fire team. Thanks for the response.