Complex sentence: In 1241, Alexander Nevsky came to Sarai, befriended and bebrothered Sartaq, become his sworn brother ("anda"), and an adopted son of Batu Khan.
Split into simpler sentences: In 1241, Alexander Nevsky came to Sarai and befriended Sartaq. He became Sartaq's sworn brother ("anda"), and an adopted son of Batu Khan.