The most pressing diplomatic problem in 1869 was the settlement of the "Alabama" claims, depredations caused to the Union by the Confederate warship , built in a British shipyard in violation of neutrality rules. Secretary Hamilton Fish played the central role in formulating and implementing the Treaty of Washington and the Geneva arbitration (1872). Senator Charles Sumner, Chairman of the Senate Foreign Relations Committee led the demand for reparations, with talk of British Columbia as payment. Fish and Treasurer George Boutwell convinced Grant that peaceful relations with Britain were essential, and the two nations agreed to negotiate along those lines. To avoid jeopardizing negotiations, Grant refrained from recognizing Cuban rebels who were fighting for independence from Spain, which would have been inconsistent with American objections to the British granting belligerent status to Confederates. A commission in Washington produced a treaty whereby an international tribunal would settle the damage amounts; the British admitted regret, but not fault. The Senate, including Grant critics Sumner and Carl Schurz, approved the Treaty of Washington, which settled disputes over fishing rights and maritime boundaries, by a 50–12 vote, signed on May 8, 1871. The "Alabama" claims settlement would be Grant's most successful foreign policy achievement that secured peace with Great Britain and the United States. The settlement of the "Alabama" Claims turned Britain into America's strongest ally.