The 16th-century breech-loading model entered China around 1517 when Fernão Pires de Andrade arrived in China. However, he and the Portuguese embassy were rejected as problems in Ming-Portuguese relations were exacerbated when the Malacca Sultanate, a tributary state of the Ming, was invaded in 1511 by the Portuguese under Afonso de Albuquerque, and in the process a large established Chinese merchant community was slaughtered. The Malacca Sultanate sent the Ming a plea for help but no relief expedition was sent. In 1521 the Portuguese were driven off from China by the Ming navy in a conflict known as the Battle of Tunmen.