In 1649 and 1650, General-at-Sea Robert Blake drove the Royalist fleet under Prince Rupert from its bases in Ireland and pursued it to the port of Lisbon, where it was protected by the harbour's forts and the Portuguese king's refusal to let Blake enter the port. The Council of State decided to reinforce Blake and authorised him to seize ships from Brazil in reprisal, and to withdraw the English envoy to Portugal, whose departure in July 1650 created a state of war. In response to the Portuguese failure to expel Rupert, Blake continued to seize merchant ships entering the River Tagus from Brazil. On 24 September 1650 Blake attacked a fleet of 23 merchant vessels from Brazil and their naval escort, sinking the Portuguese Admiral and capturing the Vice-Admiral and ten of the larger merchant ships. The Portuguese court were compelled to insist that Rupert leave Lisbon harbour in September 1650, but after finding Blake waiting for him, Rupert placed his ships under the protection of Portuguese coastal forts, where he remained until December, when he escaped to the West Indies. The threat of the Royalist fleet had been neutralised by forcing it into retreat. Its strongholds in the Isles of Scilly, the Isle of Man and the Channel Islands were captured in 1651. This was followed in 1652 by the recovery of England's colonial possessions in the West Indies and North America by General George Ayscue.