The Holy League of 1717 was one of many coalitions organised by the Papal States

Papal States

The Papal State, State of the Church, or Pontifical States were among the major historical states of Italy from roughly the 6th century until the Italian peninsula was unified in 1861 by the Kingdom of Piedmont-Sardinia .The Papal States comprised territories under...

 to deal with the Ottoman threat.
This last one comprised Portugal

Portugal

Portugal , officially the Portuguese Republic is a country situated in southwestern Europe on the Iberian Peninsula. Portugal is the westernmost country of Europe, and is bordered by the Atlantic Ocean to the West and South and by Spain to the North and East. The Atlantic archipelagos of the...

, the Republic of Venice

Republic of Venice

The Republic of Venice or Venetian Republic was a state originating from the city of Venice in Northeastern Italy. It existed for over a millennium, from the late 7th century until 1797. It was formally known as the Most Serene Republic of Venice and is often referred to as La Serenissima, in...

 and Malta

Malta

Malta , officially known as the Republic of Malta , is a Southern European country consisting of an archipelago situated in the centre of the Mediterranean, south of Sicily, east of Tunisia and north of Libya, with Gibraltar to the west and Alexandria to the east.Malta covers just over in...

.

Background

Throughout the 17th century several Holy Leagues were organised by Rome, the most famous of which finally managed to defeat the Ottoman fleet at the third Battle of Lepanto

Battle of Lepanto (1571)

The Battle of Lepanto took place on 7 October 1571 when a fleet of the Holy League, a coalition of Catholic maritime states, decisively defeated the main fleet of the Ottoman Empire in five hours of fighting on the northern edge of the Gulf of Patras, off western Greece...

. However the resurgent threat of the Ottoman fleet continued until the early 18th century.

As with the previous Leagues, Rome organised the expedition, Venice financed it and a third party - usually a Catholic kingdom - was to provide the backbone of the fleet.
Given that Spain

Spain

Spain , officially the Kingdom of Spain languages]] under the European Charter for Regional or Minority Languages. In each of these, Spain's official name is as follows:;;;;;;), is a country and member state of the European Union located in southwestern Europe on the Iberian Peninsula...

 was exhausted from the War of the Spanish Succession

War of the Spanish Succession

The War of the Spanish Succession was fought among several European powers, including a divided Spain, over the possible unification of the Kingdoms of Spain and France under one Bourbon monarch. As France and Spain were among the most powerful states of Europe, such a unification would have...

, the Pope appealed to Portugal which ended up sending a fleet to the Mediterranean.

The efforts came to fruition in late July, when a combined fleet of Portuguese, Venetian, Papal and Maltese ships defeated the fleet of Kapudan Pasha Ibrahim Pasha in the Battle of Matapan

Battle of Matapan

The naval Battle of Matapan took place on 19 July 1717 off the Cape Matapan, on the coast of the Mani Peninsula in southern Greece, between the combined naval forces of Venice, Portugal, the Papal States and Malta and the Ottoman fleet, under Kapudan Pasha...

.

Aftermath

The outcome of 1717 as well as of the prior battles with the same goal, was that of restricting the Ottoman naval dominance to the eastern Mediterranean.

After the Battle of Matapan

Battle of Matapan

The naval Battle of Matapan took place on 19 July 1717 off the Cape Matapan, on the coast of the Mani Peninsula in southern Greece, between the combined naval forces of Venice, Portugal, the Papal States and Malta and the Ottoman fleet, under Kapudan Pasha...

 however, the Ottoman Empire

Ottoman Empire

The Ottoman EmpireIt was usually referred to as the "Ottoman Empire", the "Turkish Empire", the "Ottoman Caliphate" or more commonly "Turkey" by its contemporaries...

could no longer keep up with the technological race and eventually the European fleets came to dominate the whole of the Mediterranean.