A new agreement produced at the conference reduced the territorial gains promised by the treaty: Italy received Trentino-Alto Adige/Südtirol and the Julian March in addition to the occupation of the city of Vlorë and the Dodecanese Islands.

[1] The matter became closely related to contemporary efforts to obtain an alliance with Bulgaria, or at least secure its neutrality,[2] in return for territorial gains against Entente-allied Serbia.

Believing that such a move by Italy would prompt Romania to join the Entente as well against Austria-Hungary, Russian foreign minister Sergey Sazonov pursued the matter.

British Foreign Minister Edward Grey supported the idea; he said that Trieste should be added to the claim as potentially important to win over Italian public opinion on joining the war.

Expecting opposition from Sazonov, Castello asked Grey to get the Russians to let him have this without making any concessions in return as a necessary evil to attract Italy to join the Entente.

The bulk of the Italian claim, concerning acquisition of Trentino, Trieste, and Istria was likely to attract protests against handing predominantly Slav-populated territories to Italy from Frano Supilo – a dominant figure in the nascent Yugoslav Committee advocating interests of South Slavs living in Austria-Hungary.

The Committee of Imperial Defence was concerned about rising Russian naval power in the Mediterranean and it is possible, although there is no direct evidence, that this influenced the British support for the Italian claims in the Adriatic – as means to deny it to Russia.

[21] Hoping to achieve the diplomatic breakthrough in securing alliances with Bulgaria, Romania, and Greece, Grey turned Sonnino's 16 points into a draft agreement and forwarded it to Russia against protests by the Yugoslav Committee.

Sazonov objected to the draft agreement and dismissed an Italian offer of Dubrovnik as a port for South Slavs as it lacked inland transport routes.

In response, Sazonov accepted the proposal put forward by Delcassé, insisting that Italy enter the war by the end of April and leaving all treaty-related demilitarisation matters to the British Prime Minister H. H. Asquith to decide.

The agreement was signed on 26 April by Grey and ambassadors Paul Cambon, Imperiali, and Alexander von Benckendorff, behalf of the United Kingdom, France, Italy, and Russia.

[23][24] Article 1 of the treaty determined that a military agreement shall be concluded to guarantee the number of troops committed by Russia against Austria-Hungary to prevent it from concentrating all its forces against Italy.

[26][27] Article 5 awarded Dalmatia to Italy – specifically the part north of a line running northeast from Cape Planka – including cities of Zadar and Šibenik, as well as the basin of the Krka River and its tributaries in the Italian territory.

[28] Furthermore, Article 5 required demilitarisation of the coast between the Cape Planka and the Aoös River with exception of the strip between Pelješac and a point 10 kilometres (6.2 mi) southeast of Dubrovnik and in Montenegrin territory where military bases were allowed through prewar arrangements.

[31] Articles 6 and 7 gave Italy full sovereignty over Vlorë, the Sazan Island, and surrounding territory necessary for defence – requiring it to leave a strip of land west of the Lake Ohrid to allow a border between Serbia and Greece.

Italy was to represent Albania in foreign relations, but it was also required to acquiesce to its partition between Serbia, Montenegro, and Greece if the United Kingdom, France, and Russia decided so.

He demanded the Entente refrain from treaties with Hungary or Romania on borders of interest to Croatia without conferring with Serbia first, as well as requesting assurances of future political union of the Serbs, Croats, and Slovenes.

The Yugoslav Committee president Ante Trumbić met with Lord Crewe, a senior member of the British Cabinet, demanding support for unification of Croatia, Istria, and Dalmatia and then for a political union with Serbia.

[35] In 1917, Pašić and Trumbić negotiated and agreed upon the Corfu Declaration setting out a plan for post-war unification of South Slavs to counter the Italian territorial claims outlined in the Treaty of London.

Following a major retreat, the Italian forces managed to recover and mount a comeback a year later in the Battle of Vittorio Veneto at the cost of 600,000 dead, social unrest in the country and a badly damaged economy.

[31] Under the provisions of the Armistice of Villa Giusti, Italy was allowed to occupy Austro-Hungarian territory promised to her under the Treaty of London – parts of which were also claimed by the diplomatically unrecognised State of Slovenes, Croats and Serbs.

[47] The note promised Bosnia and Herzegovina, Syrmia, Bačka, the Adriatic Coast from Cape Planka to the point 10 kilometres southeast from Dubrovnik, Dalmatian islands not assigned to Italy, and Slavonia if it was captured by the Entente militarily.

The chief Italian representatives, Prime Minister Vittorio Emanuele Orlando and Sonnino demanded enforcement of the Treaty of London relying on application of the security principle, and annexation of Rijeka on the basis of self-determination.

The British and the French would not publicly endorse any claims exceeding those afforded by the treaty while privately holding Italy deserved little because of its reserved attitude towards Germany in early stages of the war.

[53] He held the treaty invalid by application of the legal doctrine of clausula rebus sic stantibus on account of fundamental changes of circumstances following the breakup of Austria-Hungary.

[54] While the British and the French representatives remained passive on the issue,[55] Wilson published a manifesto explaining his principles and appealing for sense of justice among Italians on 24 April 1919.

[58] Orlando's and Sonnino's inability to secure all the territory promised by the Treaty of London or the city of Rijeka produced a sense that Italy was losing the peace.

Orlando's successor as Prime Minister, Francesco Saverio Nitti, decided to pull out occupying Italian troops from Rijeka and hand the city over to the inter-Allied military command.

That prompted D'Annunzio to lead a force consisting of veterans and rebelling soldiers (with the support of regular troops deployed in the border area) in what became known as the Impresa di Fiume to the successful capture of Rijeka.

[63] It comprised settlement of the border awarding Italy territory on the Snežnik Plateau north of Rijeka and a strip of land between the city and Italian-controlled Istria.