The first war, also called the Thirty Days' War, took place against a background of growing Greek concern over conditions in Crete, which was under Turkish domination and where relations between the Christians and their Muslim rulers had been deteriorating steadily. The outbreak in 1896 of rebellion on Crete, fomented in part by the secret Greek nationalistic society called Ethniki Etairia, appeared to present Greece with an opportunity to annex the island. By the beginning of 1897, large consignments of arms had been sent to Crete from Greece. On January 21 the Greek fleet was mobilized, and in early February Greek troops landed on the island, and union with Greece was proclaimed. The following month, however, the European powers imposed a blockade upon Greece to prevent assistance being sent from the mainland to the island. They took this step to prevent the disturbance from spreading to the Balkans. Thwarted in their attempt to assist their compatriots in Crete, the Greeks sent a force, commanded by Prince Constantine, to attack the Turks in Thessaly (April). By the end of April, however, the Greeks, who were inadequately prepared for war, had been overwhelmed by the Turkish army, which had recently been reorganized under German supervision. The Greeks then yielded to pressure from the European powers, withdrew their troops from Crete, and accepted an armistice on the mainland (May 20, 1897). A peace treaty, concluded on December 4, compelled Greece to pay the Turks an indemnity, to accept an international financial commission that would control Greek finances, and to yield some territory in Thessaly to Turkey. Subsequently, the Turkish troops also left Crete, which had been made an international protectorate, and an autonomous government under Prince George, the second son of the Greek king, was formed there (1898). Crete was finally ceded to Greece by the Treaty of London (1913), which ended the First Balkan War.