Can Ukraine hold on to the territory it's occupying?

It’s been over two weeks since Ukraine began its military incursion into western Russia.

Ukrainian officials have been discussing the prospect of a buffer zone between the two countries. Ukraine claims to control more than 400 miles of Russian territory.

Meanwhile, Russia’s war effort continues, with airstrikes over much of Ukraine, killing six people.

Can Ukraine manage to hold on to the territory it’s occupying?