What historical parallel concerns European leaders and Washington officials regarding the Russia-Ukraine conflict?

Many in Washington and Europe worry that current negotiations regarding Ukraine may mirror the appeasement policies of 1938, when British Prime Minister Chamberlain and French Prime Minister Daladier made a deal with Hitler that gave away part of Czechoslovakia. Within a year, Czechoslovakia was completely conquered by Germany, and World War II soon followed. This historical parallel represents a nightmare scenario for European leaders, Washington officials, and especially Ukrainian President Zelensky, who fears that a similar deal might be struck where Ukraine loses part of its territory. These concerns have intensified following recent meetings between Russian and American officials, with worry that Ukraine's interests might be sacrificed in broader geopolitical negotiations.