This shooting war has been ongoing since 2014 when the US and NATO engineered a coup against an elected, pro-Russian Ukrainian government that spawned the separatist movement in the Donbas and the Russian annexation of Crimea. Zelensky campaigned as the “Peace President” to end the war.
Despite the red lines put forth by Russia that it would not allow Ukraine to become part of NATO, we pushed forward with that objective including having Ukrainian troops trained by NATO and participating in NATO war exercises. You cannot view the current Russian invasion without viewing it in historical context.
2014 was no coup
In Feb 2014 people revolted against the Russian-backed thugs. That is known as Maidan Uprising in Kyiv. The uprising was sparked by the Ukrainian government decision to not sign a trade agreement with EU but to sign one with Russia instead (more corruption, more theft, more Russian brainwashed stupidity, brutality and gold toilets for the elite). People wanted democracy, no more Russia and no more corruption. Some 130 people died in those protests, mostly protesters and 18 cops killed by the protesters. The Russian government puppet thugs were ousted and some imprisoned for theft of state property, all in Feb 2014.
In retaliation, Putin brought in his tanks to Crimea and literally under the gun conducted a pole if the residents wanted to join Russia. Most voted for joining Russia. Crimea was annexed that way without any agreement from Ukraine. Putin also started the trouble in Donbas, a coal-rich, highly industrialized area of Ukraine coveted by several of his oligarchs. Ukrainians did not have much of a military, since everything was stolen and sold elsewhere by the previous Russian-backed crims, and could not defend Crimea but they dug in and refused to let Donbas go. Thus the war in Donbas started. Putin supported that war with supplies and troops and kept it going and it is still ongoing.
The new government of Ukraine finally got to work in 2014 creating a nation, uprooting corruption. creating structures and protocols of a free society. As a part of that process, the military was being overhauled or really created with the US help. That military had plenty of troops but not enough equipment and hardware but it was becoming a true military force. That only started in 2014 and it took some time to overcome the cynicism, corruption and the inertia of the previous era but those were overcome.