These reforms made Spain confident enough to attempt the recovery of territories in Italy ceded to Savoy and Charles VI of Austria. In 1717, a Spanish force occupied Sardinia unopposed; neither Austria or Savoy had significant naval forces and Austria was engaged in the Austro-Turkish War of 1716–18. This assumed the British would not intervene but when 38,000 Spanish troops landed on Sicily in 1718, Britain declared it a violation of Utrecht. On 2 August 1718, Britain, France, the Netherlands and the Austrians formed the Quadruple Alliance and on 11 August the Royal Navy destroyed a Spanish fleet off Sicily at the Battle of Cape Passaro.