Greek Independence, on an institutional diplomatic level, was gradually gained through a series of international Treaties and Protocols, the main ones being:
Treaty of London,
6 July 1827
Copy of the Treaty of London between the three Great Powers (United Kingdom, France, Russia), which provided for the autonomy of Greece, with the obligation to pay a tax to the Sultan. The land border was not defined, but it would be settled by a negotiation between the Contracting Parties. By a secret protocol, the Sublime Porte was given a one-month deadline to accept the terms of the Treaty, after which the fleets of the Great Powers would have the right to enforce its application.
10/22 March 1829
6/18 May 1829
British Resident to the Greek Government Edward Dawkins sends to Governor Ioannis Kapodistrias a copy of the London Protocol of 22 March 1829 and explains its basic terms and objectives regarding the question of Greece: Greece would be under the sovereignty of the Sublime Porte to which it would pay an annual tax of 1,500,000 groschen. The land border would be the Ambracian-Pagasetic line and Greece would have a Christian hereditary ruler.
Treaty of Adrianople,
2/14 September 1829
29 October 1829
The Resident of Russia to the Greek Government, Count V.N. Panin, delivers to the Governor of Greece Ioannis Kapodistrias the Treaty of Adrianople, signed on 14 September between Russia and the Ottoman Empire, and conveys the satisfaction of the Czar for its signing. According to article 10 of this Treaty, the Ottoman Empire accepted both the Treaty of London of 1827 and the London Protocol of 10/22 March 1829 and, therefore, the definition of the Ambracian-Pagasetic line as the land border between the two States.
22 January / 3 February 1830
Copy of the London Protocol, i.e. the main Protocol of Independence, as delivered to the Sublime Porte by the Ambassadors of the Great Powers on 8 April 1830. It is the first formal international act recognizing Greece as an entirely independent state. The territory of the State was reduced in relation to the Protocol of 1829 and the border was defined by rivers Acheloos to the west and Spercheios to the east, while Sporades and Euboea islands were also included in the new State. In another Protocol of the same day, Prince Leopold of Saxe-Coburg was nominated Prince-Sovereign of Greece.
The Protocol on the website of the Ministry of Foreign Affairs (in French).
Treaty (Arrangement) of Constantinople,
9/21 July 1832
19/31 July 1832. The Residents of the Great Powers inform the Minister of Foreign Affairs of the Greek Government, Spyridon Trikoupis, that the Treaty of Constantinople on the final arrangement of issues between Greece and the Ottoman Empire was signed by the latter and the three Powers. The three Residents “confidentially” send to Trikoupis a copy of the Treaty articles relating to the delimitation of the border between the two States. Translation of the letter in Greek. The Treaty defined the Arta-Volos line as the northern border of Greece, while the decision on ownership of the Lamia region, on which no agreement was reached, was referred to further negotiations. The outcome of these negotiations was the London Protocol of 18/30 August 1832, which accorded the region to Greece.
The Treaty on the website of the Ministry of Foreign Affairs (in English).