Many early Rus' principalities were virtually razed or severely affected by a major Mongol invasion in the 13th century, but the lands of modern-day Belarus avoided the brunt of the invasion and eventually joined the Grand Duchy of Lithuania. There are no sources of military seizure, but the annals affirm the alliance and united foreign policy of Polotsk and Lithuania for decades. Trying to avoid the Tatar Yoke, the Principality of Minsk sought protection from Lithuanian princes further north and in 1242, the Principality of Minsk became a part of the expanding Grand Duchy of Lithuania.