Many Spanish expeditions were sent to survey the American coasts in the 16th century. These explorations were soon followed by numerous expeditions for trade and for populating the newly discovered areas. More and more supplies and equipment were delivered to the New World. In time, the ships that were used for exploration were insufficient for the increasing volume of traffic between Spain and America, and it became necessary to design and build a new type of ship with more cargo capacity, defense capabilities and better maneuverability. It was during this period that Spanish galleons arose. It was the captains of the Spanish navy, Pedro Menéndez de Avilés and Álvaro de Bazán, who designed the definitive long and relatively narrow hulled galleon for Spain in the 1550s.