The US Army motto, signifying their willingness to execute their duties as soldiers within the US Armed Forces; This refers to the US, the Constitution, and its constituents. We'll refers to the Army's collective ideal of teamwork within soldiers. Defend refers to the Army's main task - being to defend the United States from enemies, both foreign and domestic, as well as support and defend the Constitution.
A phrase that has been ironically quoted by many vtubers after a Twitter user posted screenshots of an alleged vtuber asking for free art saying "I'm a vtuber and you'll regret this" after the artist refused.
The only real comeback to ya mum that isn't whining about how infantile your insulter is. We can only assume what is meant by 'this'.
Scenario 1-boring, slightly civilised
Tony: What are you doing tonight?
Gordon: ya mum!
Tony: Now do we really have to resort to this childishness?
Gordon: Does ya mum have to resort to childishness?
Scenario 2- Childish, good
Tony: What are you doing tonight?
Gordon: ya mum!
Tony: keep my mum out of this and I'll keep this out of ya mum
Gordon: Yes, master.