 Complete the following phrase:  At that point, the three Great PowersRussia, Britain and Francedecided to intervene, sending their naval squadrons to Greece in 1827. Following news that the combined OttomanEgyptian fleet was going to attack the island of Hydra, the allied fleets intercepted the Ottoman navy and won a decisive victory at the Battle of Navarino. In 1828 the Egyptian army withdrew under pressure of a 