on (one's) watch
on (one's) watch
Under one's supervision; while one is in a position of power, authority, or responsibility. I can't believe you let this happen on your watch. It's strange—even though it wasn't on my watch, I still feel partly responsible for the robbery.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
on someone's watch
while someone is on duty; while someone is supposed to be in charge of a situation. I am not responsible since it didn't happen on my watch. I guess I have to bear the blame since it happened on my watch.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.
on someone's watch
COMMON If something bad happens on someone's watch, it happens during a period when they are in a position of power, and are therefore responsible for it. Mistakes were made on my watch, and accordingly I believe my decision to resign, while painful, is appropriate. The last two sitting Democratic presidents suffered enormous political damage from foreign policy disasters that occurred on their watch. Note: When someone such as a soldier is on watch, they have been ordered to remain alert, usually while others sleep, so that they can warn of danger or an attack.
Collins COBUILD Idioms Dictionary, 3rd ed. © HarperCollins Publishers 2012