The best option to preserve Ukrainian sovereignty and independence is to push Russian forces back into Russia, Belarus, and Moldova.
The breakup of the Yugoslavia was a smaller version of what is happening in the old domains of the USSR.
Yugoslavia was a facade for a Greater Serbia. In the 1990s, Serbia fought in Croatia, Bosnia, and Kosovo re-assert its previous dominance of the emerging independent nation states of the Slovenians, Croats, Bosnians, Montenegrans, Kosovars, and Macedonians.
The breakup of Yugoslavia was partially driven by the desire of emerging indpenedent nation states wanting to leave Serbia's obrbit to joing the E.U. Serbia has historically been a proxy for Russian national interests in the Balkans.
Ukraine is trying to breakaway from Russia's orbit to join the E.U., and join NATO if that's what is required to maintain independence from Russia, Russian interference, Russian influenece, and Russian dominance. Russia is desperately trying to stop it, much like Serbia tried to stop Slovenia, and Croatia. Croatia was a buffer between Slovenia and Serbia. Croatia conceded Slavonia to Serbia to gain its independence. Putin is pursuing a similar policy with Ukraine, but cannot tolerate it. Croatia and Slovenia later joined NATO, in addition to the E.U., partially out of concern that they were not safe from Serbian and Russian designs for them.
Russia wins if keeps conquered territory and the Ukranians reject joining the E.U. and N.A.T.O. If Ukraine does not become a member of the E.U., it is doomed to become a Putin satellite state, like Belarus and Moldova.
