Yugoslavia was quickly overwhelmed by the combined strength of the Axis powers and surrendered in less than two weeks. The government and royal family went into exile, and the country was occupied and dismembered by its neighbours. The German-occupied territory of Serbia was reduced to the Kingdom of Serbia's pre-Balkan War borders and was kept under directly military occupation by the Germans due to the key rail and riverine transport routes that passed through it, as well as its valuable resources, particularly non-ferrous metals. The occupied territory covered about 51,000 km2 and had a population of 3.8 million. The Germans began searching for a Serb suitable to lead a puppet government in Belgrade.