Romania in World War I
The Kingdom of Romania was neutral for the first two years of World War I, entering on the side of the Allied powers from 27 August 1916 until Central Power occupation led to the Treaty of Bucharest in May 1918, before reentering the war on 10 November 1918. It had the most significant oil fields in Europe, and Germany eagerly bought its petroleum, as well as food exports.
From the point of view of its belligerent status, Romania was a neutral country between 28 July 1914 and 27 August 1916, a belligerent country on the part of the Entente from 27 August 1916 to 9 December 1917, in a state of armistice with the Central Powers from 10 December 1917 to 7 May 1918, a non-combatant country between 7 May 1918 and 10 November 1918, and finally a belligerent country in the Entente between 10 and 11 November 1918.
At the start of World War I, King Carol I of Romania favored Germany, while the nation's political elite favored the Entente. As such, the crown council decided to remain neutral. But after King Carol's death in 1914, his successor King Ferdinand I favored the Entente. For Romania, the highest priority was taking Transylvania from Hungary, which had around 2.8 milion Romanians, among approximately 5 milion other people. The Allies wanted Romania to join their side in order to cut rail communications between Germany and Turkey, and to cut off Germany's oil supplies. Britain made loans, France sent a military training mission, and Russia promised modern munitions. The Allies promised at least 200,000 soldiers to defend Romania against Bulgaria to the south, and help it invade Austria-Hungary.
At the outbreak of hostilities, the Austro-Hungarian Empire invoked a casus foederis on Romania and Italy linked to the secret treaty of alliance since 1883. However, both Italy and Romania refused to honor the treaty on the grounds that it was not a case of casus foederis because the attacks on Austria were not "unprovoked", as stipulated in the treaty of alliance. In August 1916, Romania received an ultimatum to decide whether to join the Entente "now or never". Under the pressure of the ultimatum, the Romanian government agreed to enter the war on the side of the Entente, although the situation on the battle fronts was not favorable.
The Romanian campaign was part of the Eastern Front of World War I, with Romania and Russia allied with Britain and France against the Central Powers of Germany, Austria-Hungary, the Ottoman Empire, and Bulgaria. Fighting took place from August 1916 to December 1917 across most of present-day Romania, including Transylvania, which was part of the Austro-Hungarian Empire at the time, as well as in Southern Dobruja, which is currently part of Bulgaria.
The Romanian campaign plan (Hypothesis Z) consisted in attacking Austria-Hungary in Transylvania, while defending Southern Dobruja and Giurgiu from Bulgaria in the south. Despite initial successes in Transylvania, after German divisions started aiding Austria-Hungary and Bulgaria, the Romanian forces (aided by Russia) suffered massive setbacks, and by the end of 1916 out of the territory of the Romanian Old Kingdom only Western Moldavia remained under the control of the Romanian and Russian armies.
After several defensive victories in 1917 at Mărăști, Mărășești, and Oituz, with Russia's withdrawal from the war following the October Revolution, Romania, almost completely surrounded by the Central Powers, was also forced to drop out of the war. It signed the Treaty of Bucharest with the Central Powers in May 1918. Under the terms of the treaty, Romania would lose all of Dobruja to Bulgaria, all the Carpathian passes to Austria-Hungary and would lease all of its oil reserves to Germany for 99 years. However, the Central Powers recognized Romania's union with Bessarabia who had recently declared independence from the Russian Empire following the October Revolution and voted for union with Romania in April 1918. The parliament signed the treaty, but King Ferdinand refused to sign it, hoping for an Allied victory on the western front. In October 1918, Romania renounced the Treaty of Bucharest and on 10 November 1918, one day before the German armistice, Romania re-entered the war after the successful Allied advances on the Macedonian front and advanced in Transylvania. The next day, the Treaty of Bucharest was nullified by the terms of the Armistice of Compiègne.
Map of the Treaty of Bucharest (1916), 10 days before Romania's entry to the war. The Entante's promises are highlighted in yellow.
The extent of Romania's advance into Transylvania before the counteroffensive of the Central Powers.
Romanian invasion of Austria-Hungary, August 1916
Central Powers counterattack, September–October 1916
Operations in Romania, November 1916 to January 1917
Operations in Dobruja, 19 October to 11 November 1916
Romanian front, 12 January 1917
The 1916 counteroffensive was mainly led by the German generals Falkenhayn and Mackensen.[101] Despite this the Germans represented only 22% of the Central Power's forces that took part in the campaign compared to the Austro-Hungarian 46% and combined Bulgarian and Ottoman 32%.[102]
In his 1922 book, A History of the Great War: From the Battle of Verdun to the Third Battle of Ypres, John Buchan provides a comprehensive analysis of the Romanian 1916 Campaign:
Erich Ludendorff summarized the end of the 1916 Romanian campaign as follows:
The failure of the Romanian front for the Entente was also the result of several factors beyond Romania's control. The failed Salonika Offensive did not meet the expectation of Romania's "guaranteed security" from Bulgaria.[105] This proved to be a critical strain on Romania's ability to wage a successful offensive in Transylvania, as it needed to divert troops south to the defense of Dobruja.[106] Furthermore, Russian reinforcements in Romania did not materialize to the number of 200,000 soldiers initially demanded.[107]