the first decades of ferdinand and isabella's joint rule were taken up with the conquest of the kingdom of granada, the last muslim bit of al-andalus. this was completed by 1492 and then the jews were expelled from both castile and aragon. the royal couple sent christopher columbus on his expedition which discover the new world. by the treaty of tordesillas of 1494, the extra-european world was split between the crowns of portugal and castile by a north-south line through the atlantic ocean.