Depending on scale of conflict carrier groups on their own can wage war as soon as they get to position. It's a fair question.

Theres elements of the Gulf War that point at that capability as the US was able to organize an armed response to defend its allies in the area really quick. While there were 5 months between loss of Kuwait and combat operations, that has to do with desire to build an arab coalition as well as obtain UN backing (which gave Iraq until january to pull their troops back anyway)

That's of course, assuming we consider Iraq a near peer. China seems a more obvious choice but at least Iraq had proven gear and troops with field experience. I dont imagine Russia would fare any better than Iraq did either.