These incidents, in which a total of 447 enslaved people belonging to US nationals were freed from 1830 to 1842, increased tension between the United States and the United Kingdom. They had been co-operating in patrols to suppress the international slave trade. However, worried about the stability of its large domestic slave trade and its value, the United States argued that the United Kingdom should not treat its domestic ships that came to its colonial ports under duress as part of the international trade. The United States worried that the success of the ''Creole'' slaves in gaining freedom would encourage more slave revolts on merchant ships.