Russian President Vladimir Putin is amassing a large force near the Ukrainian border and reportedly has a military plan to invade and conquer most of unoccupied Ukraine. Western leaders are rightly taking the threat of such an invasion very seriously, and we cannot dismiss the possibility that Putin will order his military to execute it. However, the close look at what such an invasion would entail presented in this report and the risks and costs Putin would have to accept in ordering it leads us to forecast that he is very unlikely to launch an invasion of unoccupied Ukraine this winter. Putin is much more likely to send Russian forces into Belarus and possibly overtly into Russian-occupied Donbas. He might launch a limited incursion into unoccupied southeastern Ukraine that falls short of a full-scale invasion.