Complex sentence: Some small missions in the area were founded in the 1610s and 1620s, however, the Seri Indians were strongly opposed to the settlement of Europeans and would resist fiercely until 1769.
Split into simpler sentences: Some small missions in the area were founded in the 1610s and 1620s. However, the Seri Indians were strongly opposed to the settlement of Europeans and would fight fiercely until 1769.