Question: Which treaty caused Bulgaria to loose most of its territories?
About the article "Balkan Wars", section "Abstract".

Candidate passages:
The Treaty of Neuilly-sur-Seine required Bulgaria to cede various territories, after Bulgaria had been one of the Central Powers defeated in World War I.
The treaty was signed on 27 November 1919 at Neuilly-sur-Seine, France.
The treaty required Bulgaria  to cede Western Thrace to the Entente (which awarded it to Greece at the San Remo conference) thereby cutting off Bulgaria's direct outlet to the Aegean Sea to cede a further area of on its western border with the Kingdom of Serbs, Croats and Slovenes (later Yugoslavia) to return Southern Dobruja, which had been captured during the war, to Romania, thus restoring the border set by the Treaty of Bucharest (1913) to reduce its army to 20,000 men to pay reparations of £100 million to recognize the existence of the Kingdom of Serbs, Croats and Slovenes.
The signing ceremony was held in Neuilly's town hall (hôtel de ville).
In Bulgaria, the results of the treaty are popularly known as the Second National Catastrophe.
Bulgaria subsequently regained South Dobruja as a result of the Treaty of Craiova.
During World War II, together with Nazi Germany, it temporarily reoccupied most of the other territories ceded under the treaty. 
In Bulgarian historiography, the Liberation of Bulgaria refers to those events of the Russo-Turkish War of 1877-78 that led to the re-establishment of the Bulgarian state under the Treaty of San Stefano of March 3, 1878.
According to the treaty, the Ottoman Empire was deprived of a large portion of its territory, which was assigned to the client state, Bulgaria.
At the Berlin congress of the same year, the Treaty of Berlin (1878) was adopted, according to which the territories of the Bulgarian state, established as per the San Stefano treaty, were divided into three parts: the first part was the Principality of Bulgaria, which functioned independently but was nominally a vassal of the Ottoman Empire and was limited to Moesia and areas adjacent to the capital Sofia; the second part was to be an autonomous province of the Ottoman Empire -- Eastern Rumelia; the third and largest part -- all of the Macedonia and Lozengrad -- were restored to the Ottoman Empire, while some outlands were assigned to Serbia and Romania.
Those territories seized from Bulgaria after the Berlin congress, including most of Macedonia, Thrace, etc., had a majority ethnic Bulgarian population.
On September 6, 1885, Eastern Rumelia became part of the Princiapality of Bulgaria after a bloodless unification, although the principality was a "de facto" independent nation but "de jure" vassal nation of the Ottoman Empire until 1908, when Bulgaria proclaimed its declaration of independence.
The 1908 declaration, which signified Bulgaria's break with the Ottoman rule, was actually the second liberation of Bulgaria.
After the conquest of the First Bulgarian Empire in 1018, the first liberation of Bulgaria led to the establishment of the Second Bulgarian Empire in the aftermath of the Uprising of Asen and Peter against the Byzantine Empire in 1185. 
The Second Balkan War was a conflict which broke out when Bulgaria, dissatisfied with its share of the spoils of the First Balkan War, attacked its former allies, Serbia and Greece, on 16 (O.S.
)/29 June 1913.
Serbian and Greek armies repulsed the Bulgarian offensive and counter-attacked, entering Bulgaria.
With Bulgaria also having previously engaged in territorial disputes with Romania, this war provoked Romanian intervention against Bulgaria.
The Ottoman Empire also took advantage of the situation to regain some lost territories from the previous war.
When Romanian troops approached the capital Sofia, Bulgaria asked for an armistice, resulting in the Treaty of Bucharest, in which Bulgaria had to cede portions of its First Balkan War gains to Serbia, Greece and Romania.
In the Treaty of Constantinople it lost Edirne to the Ottomans. 
The Congress of Berlin (13 June - 13 July 1878) was a meeting of the leading statesmen of Europe's Great Powers and the Ottoman Empire.
In the wake of the Russia's smashing victory in a war with Turkey, 1877–78, the urgent need was to stabilize and reorganize the Balkans, and set up new nations.
German Chancellor Otto von Bismarck, who led the Congress, undertook to adjust boundaries to minimize the risks of major war, while recognizing the reduced power of the Ottoman Empire, and balance the distinct interests of the great powers.
As a result, Ottoman holdings in Europe declined sharply; Bulgaria was established as an independent principality inside the Ottoman Empire, but was not allowed to keep all its previous territory.
Bulgaria, without being admitted to the Congress, lost more than 70% of its territory, and over 50% of its ethnic population remained outside its borders—which caused a number of uprisings and brought the country into subsequent Balkan wars.
Bulgaria lost Eastern Rumelia, which was restored to the Turks under a special administration.
Macedonia, and East and Western Thrace were returned outright to the Turks, who promised reform and Northern Dobrudja became part of Romania, which achieved full independence but had to turn over part of Bessarabia to Russia.
Serbia and Montenegro finally gained complete independence, but with smaller territories.
Austria took over Bosnia and Herzegovina, and effectively took control of the Sanjak of Novi Pazar.
Britain took over Cyprus.
The results were at first hailed as a great achievement in peacemaking and stabilization.
However, most of the participants were not fully satisfied, and grievances regarding the results festered until they exploded in world war in 1914.
Serbia, Bulgaria, and Greece made gains, but far less than they thought they deserved.
The Ottoman Empire, called at the time the "sick man of Europe," was humiliated and significantly weakened, rendering it more liable to domestic unrest and more vulnerable to attack.
Although Russia had been victorious in the war that occasion the conference, it was humiliated at Berlin, and resented its treatment.
Austria gained a great deal of territory, which angered the South Slavs, and led to decades of tensions in Bosnia and Herzogovina.
Bismarck became the target of hatred of Russian nationalists and Pan-Slavists, and found that he had tied Germany too closely to Austria in the Balkans.
In the long-run, tensions between Russia and Austria-Hungary intensified, as did the nationality question in the Balkans.
The congress was aimed at the revision of the Treaty of San Stefano and at keeping Constantinople in Ottoman hands.
It effectively disavowed Russia's victory over the decaying Ottoman Empire in the Russo-Turkish War.
The Congress of Berlin returned to the Ottoman Empire territories that the previous treaty had given to the Principality of Bulgaria, most notably Macedonia, thus setting up a strong revanchist demand in Bulgaria that in 1912 was one of many causes of the First Balkan War. 
The peace treaty between Russia and the Ottoman Empire was signed at San Stefano, on 3 March 1878.
Russia did not keep its promises of the 4 April 1877 treaty (signed by the Russian consul Stuart Dimitri (and approved by the Czar Alexander II and the Romanian Prime Minister of the day Mihail Kogălniceanu) to respect Romania's territorial integrity.
However, the treaty was not recognised by the Central Powers and the 1878 peace conference in Berlin decided that Russia would give Romania its independence, the territories of Dobrogea, the Danube Delta and access to the Black Sea including the ancient port of Tomis (Constantza), as well as the tiny Snake Island (Insula Şerpilor), but Russia would nevertheless occupy as a so-called "compensation" the old Romanian Southern counties of Bessarabia (Cahul, Bolgrad and Ismail), which by the Treaty of Paris of 1856 (after the Crimean War) were included in Moldavia.
Prince Carol was most unhappy by this imposition of Russian occupation of Romanian territories that seriously breached the Russo-Romanian treaty of 4 April 1877; he was finally persuaded by Bismarck (in now-published original letters exchanged at that time) to accept this compromise with Russia in view of the great economical potential of Romania's direct access to the Black Sea and its ancient ports at the expense of Bulgaria.