It's hard to imagine Ukraine breaking through those entrenchments though. They are going to attract a lot of aggression there.

So that 1200-mile border is a problem for Russia to defend as well as Ukraine.

Ukraine may or may not be able to use the F-16's as air support there. There are restrictions inside Russia, and they'll have to thread the needle. But they will be damn hard to repel with air superiority.

there’s even been an incursion on Russian territory since WWII.

simple fact.