be wise after the event
US /biː waɪz ˈæftər ðə ɪˈvent/
UK /biː waɪz ˈæftər ðə ɪˈvent/
1.
to understand what should have been done only after something has happened
:
•
It's easy to be wise after the event, but we made the best decision we could at the time.
•
He always tends to be wise after the event, pointing out mistakes when it's too late.