In the Atlantic, the West India Company concentrated on wresting from Portugal its grip on the sugar and slave trade, and on opportunistic attacks on the Spanish treasure fleets on their homeward bound voyage. Bahia on the north east coast of Brazil was captured in 1624 but only held for a year before it was recaptured by a joint Spanish-Portuguese expedition. In 1628, Piet Heyn captured the entire Spanish treasure fleet, and made off with a vast fortune in precious metals and goods that enabled the Company two years later to pay its shareholders a cash dividend of 70%, though the Company was to have relatively few other successes against the Spanish. In 1630, the Dutch occupied the Portuguese sugar-settlement of Pernambuco and over the next few years pushed inland, annexing the sugar plantations that surrounded it. In order to supply the plantations with the manpower they required, a successful expedition was launched in 1637 from Brazil to capture the Portuguese slaving post of Elmina, and in 1641 successfully captured the Portuguese settlements in Angola. In 1642, the Dutch captured the Portuguese possession of Axim in Africa. By 1650, the West India Company was firmly in control of both the sugar and slave trades, and had occupied the Caribbean islands of Sint Maarten, Curaçao, Aruba and Bonaire in order to guarantee access to the islands' salt-pans.

Answer this question based on the article: Who did the West India Company attack?j
Spanish treasure fleets