The Battle of Westerplatte was the very first battle that took place after Germany invaded Poland and World War II began in Europe.
During the first week of September 1939, a completely surrounded Military Transit Depot (Wojskowy Skład Transportowy, WST) on the peninsula of Westerplatte, manned by only less than 200 Polish soldiers, held out for seven days (several times longer than they were ordered to) in the face of an overwhelming force of thousands of German troops attacking from land, sea and air.
The heroic defense of Westerplatte served as an inspiration for the country when the successful German advances continued elsewhere in Poland and nowadays is still regarded as a symbol of the invasion.