Two cities in one, Wroclaw combines a German past with a Polish present. Initially an isle-based market town under no particular ruler, Wroclaw was blessed with a bishopric from the new Polish nation almost a millenium ago. But this early claim by Poland quickly came under attack when a century later the Poles effectively fought off the Germans. Their defeat, this time, was so decisive that Henry V's troops exited too quickly to gather up their dead and dying, leaving them as fodder for the dogs. Hence even today the battlefield is called 'Dog's Field'.
Failure on the battlefield was followed by a different type of advance: Germans began settling in the area, and their strength in numbers proved sufficient to rename Wroclaw 'Breslau' when this region fragmented into independent duchies in the following century. Connections with the west deepened when Breslau joined the Hanseatic League, and its bishop became a prince under the Holy Roman Empire.
This changing of hands continued until the present day: in 1335, the Bohemian kings took over, then in 1526 the Austrian Hapsburgs, and finally in 1763 the Prussians. At this point, Breslau tolerantly contained a mixed religious and ethnic population, but it developed into a predominantly German city.
So German that when WWII wound down, Nazis spent 4 months under siege here, leaving 70% of the town in ruins when the Soviets finally broke through. And, so German that Poland did not claim it when the war ended; its tiny Polish population and centuries-long rule by others left it without strong ties to the newly-drawn Poland. Its transfer arose from compromise. The Soviets got some of the east, and to compensate, Poland got some of the west. The now-Ukrainian town of L'viv (once Lwow) emptied of Poles who then moved on to fill the equally emptied Wroclaw. Since the war, Wroclaw has been rebuilt and now displays its long multinational tradition in industry and architecture.