He was born in Vlissingen in 1597 or 1599. Early in his career he was active against the Dunkirkers and was promoted to captain in 1624. That year he took service for the Zeeland Chamber of the Dutch West India Company (WIC), remaining there until 1636. He defeated four Spanish Galleons in 1626 when commander of a squadron of three ships taking or sinking three of them, he also repeatedly defeated the Dunkirk corsairs Banckert often fought together with Piet Hein with whom he attacked and captured the Portuguese settlement Salvador on the coast of Brazil in 1624 and as a Vice Admiral helped capture the Spanish treasure fleet in the Bay of Matanzas in 1628. Thanks to these and other feats he earned the nicknames "Scourge of the Marranos" (the latter word then being used as a pejorative nickname for the Spanish in general) and "Terror of the Portuguese".