Horses crossed the Baltic Sea in ships during the Late Viking Age and were sacrificed for funeral rituals. Studies on the remains of horses found at ancient burial sites in Russia and Lithuania show that they were brought overseas from Scandinavia utilizing expansive trade networks connecting the Viking world with the Byzantine and Arab Empires. Up to now, researchers had believed sacrificial horses were always locally-sourced stallions. But these results reveal horses from modern Sweden or Finland traveled up to 1,500 km across the Baltic Sea. The findings also show that the sex of the horse was not necessarily a factor in them being chosen for sacrifice, with genetic analysis showing one in three were mares.