During the colonial era, the powers of Europe sought to carve new colonies for themselves. This was made possible geographically because West Africa's coast is on the Atlantic Ocean, making it both open to cultural and trade influences, as well as to conquest by sea. West Africa is rich in many precious metals, minerals and products, which invites the interest and competition of outside powers and influences. There were some bloody conflicts in the 20th century when some of these nations fought against the colonial powers, such as during the Guinea-Bissau War of Independence (1963–1974).