What does the expression «flag in your hands» mean?
If someone wishes you luck in a hopeless endeavor, they might say: “Флаг вам в руки!” (“Flag vam v ruki” or "Flag in your hands!")
It entered literary Russian from the military sphere. Standard-bearers and drummers usually marched in the front ranks during an offensive and everyone else looked up to them. But, they also took the most risks.
Over time, this expression came to be used ironically, for example, when it was necessary to emphasize the futility of an undertaking.
An English equivalent would be: “Knock yourself out!”
