Treaty of Bucharest ( 1916 ) The Treaty of Bucharest of 1916 was signed between Romania and the Entente Powers on 4 ( Old Style ) / 17 ( New Style ) August 1916 in Bucharest . The treaty stipulated the conditions under which Romania agreed to join the war on the side of the Entente , particularly territorial promises in Austria - Hungary . The signatories bound themselves to keep secret the contents of the treaty until a general peace was concluded . Negotiations . In 1915 Lieutenant - Colonel Christopher Thomson , a fluent French speaker , was sent to Bucharest as British military attaché on Kitchener ' s initiative to bring Romania into the war . But when there he quickly formed the view that an unprepared and ill - armed Romania facing a war on three fronts against Austria - Hungary , Turkey and Bulgaria would be a liability not an asset to the allies . This view was brushed aside by Whitehall , and he signed ( with foreboding ) a Military Convention with Romania on 13 August 1916 . Thompson became head of the British Military Mission . Treaty . The treaty had two parts : a political treaty ( seven articles ) and a military convention ( seventeen articles ) . The Romanian government was to declare war on Austria - Hungary — in accordance with the stipulations in the military convention — on August 28 ( new style ) the latest , and according to the political treaty , in exchange it was to receive the following territories : The exact borders stipulated by the treaty were those of prewar Romania ( Article I ) plus those it was allowed to annex from Austria - Hungary , up to a line of demarcation described in Article IV : In article IV Romania also bound itself not to construct fortifications opposite of Belgrade , and to indemnify Serbs from Banat for their properties if they emigrated from Romania in the two years following the conclusion of peace . In Article V of the political convention , the signatories promised not to make separate peace , and also bound Great Britain , France , Italy and Russia to let Romania annex the territories from article IV at an eventual Peace Treaty . The Entente also guaranteed Romania equal rights with its allies at the Peace Conference in article VI of the political treaty . Article VII bound the signatories to maintaining secrecy of the convention until a general peace was signed . The military convention stated that Romania was to attack Austria - Hungary from the south , while Russia committed itself to start an offensive on the Austrian front in order to support the Romanian advance into Transylvania . Also the Russian High Command promised to send two infantry divisions and one cavalry division into Dobruja to protect the rear of the front from a Bulgarian attack . The French and the British pledged to start an offensive on the Thessaloniki front in order to force Bulgaria out of the war . Romania enters the war . In the morning of 14 / 27 August , a Crown Council was held at the Cotroceni Palace , convened by King Ferdinand . The Council decided to honor the Treaty with the Entente Powers , and on 27 August , Romania declared war on Austria - Hungary , and launched three armies of 440 , 000 men the same night across the passages of the Southern Carpathians . The advance of the Romanian Army was unopposed , as Austria - Hungary did not station considerable forces along the Romanian border . By mid - September , however , the attack was halted , as German - Bulgarian troops advanced into Dobruja and threatened to outflank the Romanian Army from the south - east . In October the Romanian Army was pushed out of Transylvania with the help of German reinforcements . By the end of 1916 the capital Bucharest fell — along with Wallachia and Dobruja — under the control of Central Powers and the Romanian government retreated to Iaşi . Thompson , now head of the British Military Mission , had to alleviate the consequences of Romania ’ s capitulation , and he personally supervised the destruction of the Romanian oil wells to deny them to Germany . In 1917 , the Romanian Army recovered and succeeded to stop the German attempts to break the front , in spite of the disintegration of the Russian Army after the February Revolution . The toll of the campaign was approximately 220 , 000 dead for Romania , but in the end it gained Transylvania , two - thirds of the Banat , Bukovina and Bessarabia .