The Third Armada, which departed in April 1501 under João da Nova was smaller, with four ships and, perhaps, a supply ship to be dismantled along the way but events in eastern waters meant that the Fourth was much larger.
Twenty vessels in three squadrons under da Gama departed in February and April 1502.
Cabral's fleet had reached India in just six months, discovered Brazil along the way (though that may have been the official announcement of previously undisclosed landfalls) and established Portugal's first trading post in India. The primary goal of the expedition, a treaty with the Zamorin and a Portuguese factory in Calicut, however, failed to eventuate.
While Cabral did manage to get his factory there, conflict with local Arab merchant guilds, saw it overrun in a riot with as many as seventy Portuguese killed. Cabral bombarded the city and withdrew. He did, however, manage to arrange an alliance with the ruler of Cochin and establish a factory there, and open relations with Cannanore, Cranganore and Quilon before he departed for Europe in January 1501. Cabral arrived home in July.
In the meantime João da Nova had departed, so the reaction to the setbacks Cabral encountered would fall to da Gama's Fourth Armada.
Da Gama commanded a squadron of ten ships, with support from two flotillas of five ships commanded by his uncle Vicente Sodré and cousin Estêvão da Gama. The main fleet and the first support flotilla sailed in February 1502, called at the Cape Verdes and arrived in Sofala in East Africa in June. After establishing a factory in Mozambique, extorting tribute from the ruler of Kilwa, and negotiating a treaty with the ruler of the gold trading port of Sofala, they combined with Estêvão da Gama's five ships, which had left home in April, at Malindi in August 1502.