Complex sentence: The German policy for German Expansion was actually planned in so called "Generalplan Ost" to continue farther eastwards into Poland, the Baltic states and the Soviet Union, thus creating a Greater Germany from the North Sea to the Urals.
Split into simpler sentences: The German policy for German Expansion was actually planned in so called "Generalplan Ost" to continue farther eastwards into Poland, the Baltic states and the Soviet Union. Thusly creating a Greater Germany from the North Sea to the Urals.