 De Witt was, however, prepared to act alone against Sweden in 1655 and, jointly with Denmark, again in 1658.Although the Commonwealth was an ally of Sweden, it did not come to the aid of its ally, even when the Dutch thwarted the Swedish attempt to conquer Denmark in the battle of the Sound on 8 November 1658.De Witt's aim was to establish peace in the Baltic for the benefit of Dutch commerce there.