Mecklenburg was ravaged by the thirty years' war. It suffered by the hands of the Swedish soldiers as well as by those of Imperial armies. Out of fear no crops were grown, causing starvation upon which pest broke out. Many succumbed to hunger and disease; probably 8,000
people died in the city of Neubrandenburg and about 20,000 in Guestrow.
In 1643 the Swedes again went through Mecklenburg, to be followed by the Imperial army, only to have this repeated in 1645. When in 1648 a treaty was signed in M?nster, the population of Mecklenburg had been reduced from 300,000 to about 50,000.
Adolf Friedrich I, who was Duke in these appalling times, was able to add the counties of Schwerin and Ratzeburg to his territories. His first marriage had brought him eight children, of which six reached maturity, while his second marriage brought him another eleven of which also six survived.

Source: Leo van de Pas