Appeasement failed as a strategy in the lead-up to WWII for a few reasons. Firstly, it emboldened countries like Germany to take increasingly aggressive actions, confident that they would not face confrontation from the West. This ultimately led to Germany's invasion of Poland, which resulted in war. Secondly, the West underestimated the true intentions and ambitions of Nazi Germany, which ultimately led to a disastrous misjudgment.
In the current day, the United States should learn from the failure of the appeasement strategy in the lead-up to WWII. The situation in Ukraine could be similarly escalated, should the United States or other western powers underestimate the intentions of Russia or encourage them with a lack of strong response. Any appeasement would risk a dangerous cycle of continuing aggression and insecurity, leaving millions of people living under the shadow of conflict, as in Ukraine. Therefore, it is important that the United States and other Western nations remain vigilant and act decisively against any moves that threaten peace and stability in the region.