Romania in World War 1: Why It Joined in 1916 and Lost Bucharest
Romania entered World War 1 on 27 August 1916 on the side of the Entente, lured by a promise of Transylvania, and was overrun within four months: Bucharest fell on 6 December 1916 and the country lost its capital, most of its territory and its oil wells. Yet Romania was on the winning side in 1918 and doubled in size at the peace. The short version: a late, badly timed entry, a catastrophic 1916 and a surprising recovery.
This article is for readers who want a clear account of why Romania joined, why the campaign collapsed, and why oil and supply lines mattered more than the number of soldiers, including what that means for a strategy game set in 1914-1918.
Why Romania stayed neutral until 1916
In 1914 Romania was formally allied with Germany and Austria-Hungary through a secret treaty signed in 1883, but after King Carol I died in October 1914 his successor Ferdinand and the government did not feel bound by it, because the treaty only covered a defensive war. Romania declared neutrality in August 1914, a position we cover in our overview of neutral countries in World War 1.
Neutrality was a bargaining chip. About 3 million Romanians lived in Austria-Hungary, mostly in Transylvania, and Bucharest wanted them inside its borders. Both sides courted the country for two years. Prime Minister Ion I. C. Brătianu waited until he could see who was winning.
The 1916 decision: Brusilov and the secret treaty
The moment came in the summer of 1916. The Russian Brusilov Offensive, launched on 4 June, had smashed Austro-Hungarian armies in the east (see the Eastern Front), while Germany was bleeding at Verdun and on the Somme. Austria-Hungary looked close to collapse, as described in our article on why the empire fell apart.
On 17 August 1916 Romania signed a secret convention with the Entente promising Transylvania, Bukovina and the Banat if it joined. Ten days later, on 27 August, it declared war on Austria-Hungary. Its army was about 650,000 men on paper, but it had few machine guns, little heavy artillery and almost no modern air or medical support.
Why the campaign collapsed
Romania's plan was to invade Transylvania across the Carpathians while holding its long southern border along the Danube. That was the mistake: its frontier was roughly 1,500 km long and could not be defended everywhere.
- Two enemies at once. In September a German-Bulgarian-Ottoman army under August von Mackensen attacked from the south, and the border fortress of Turtucaia (Tutrakan) fell in early September with about 25,000 prisoners and casualties.
- German reinforcements from the west. Erich von Falkenhayn, the dismissed German chief of staff, took command of the new 9th Army and pushed the Romanians back out of Transylvania through the mountain passes in October and November.
- Little help from the Entente. The promised Russian support arrived late, and the Allied offensive from Salonika, described in our article on the Balkan Front, did not tie down enough Bulgarian troops.
The Romanian counterattack at the Argeș River on 1-3 December 1916 failed at a cost of about 60,000 casualties, and Bucharest fell on 6 December. The government and the remaining army withdrew north-east to Iași in Moldavia.
The oil: why Germany wanted Romania
Romania was one of the world's major oil producers, around 1.8 million tonnes a year before the war, and Germany, cut off by the British blockade, needed fuel and grain badly. As the Central Powers closed in, Romanian and British personnel wrecked the Ploiești oil fields, burning stocks and damaging wells and refineries. Accounts differ on who did what, and the credit often given to the British mission of Colonel John Norton-Griffiths is debated.
The sabotage slowed German use of the oil for months, but did not end it. After the occupation the Central Powers also took grain, which helped them through the 1917 food crisis. The lesson is old and simple: resources decide how long an army can keep fighting, not only how many men it has.
Mărășești and the Romanian recovery
The front stabilised along the Siret River in Moldavia. With a French military mission under General Henri Berthelot reorganising the army, Romania fought three defensive battles in the summer of 1917, Mărăști, Mărășești and Oituz, and held the line against Germany's counter-offensive. These are often called Romania's finest hour of the war.
Then Russia collapsed in revolution (see how Russia left the war at Brest-Litovsk). Isolated, Romania signed the Armistice of Focșani on 9 December 1917 and the harsh Treaty of Bucharest on 7 May 1918, which gave Germany a long lease on its oil wells.
1918: the last-minute return
In autumn 1918 the Central Powers collapsed. Romania re-entered the war on 10 November 1918, one day before the Armistice, and on 1 December 1918 Transylvania voted for union with Romania at Alba Iulia. The postwar peace settlement, described in how World War 1 ended, confirmed the new borders and roughly doubled the country's territory. The price was heavy: about 335,000 Romanian soldiers killed and many more civilians dead from hunger and typhus.
What Romania's 1916 teaches about strategy
- Timing beats numbers. Romania entered when the Central Powers had just freed reserves, not when they were weakest.
- A long border is a liability. Attacking in one direction while the other flank is open invites a counter-strike.
- Resources are targets. Whoever holds the oil, grain and railways holds the war economy.
- Withdraw and regroup. Giving up the capital saved the army, which later held the Siret line.
How this plays out in Frontkrieg
In Frontkrieg, a free browser strategy game about World War 1, the same trade-offs appear in every match. Oil and other resources are covered in the economy and resources guide, the geography of fronts in the Europe 1914 map guide, and a quick overview of the whole war in the World War 1 timeline. Before opening a second front, check what it will cost you to hold it.
Frequently asked questions
Why did Romania join World War 1?
Romania joined the Entente in August 1916 mainly to gain Transylvania, Bukovina and the Banat from Austria-Hungary, where about 3 million Romanians lived. The Brusilov Offensive made Austria-Hungary look weak, and the secret treaty of 17 August 1916 promised those territories.
Why did Romania do so badly in 1916?
It faced attacks from two directions with a poorly equipped army and a very long border. German, Bulgarian and Ottoman forces struck from the south while Falkenhayn's 9th Army pushed it out of Transylvania, and Entente help arrived too late.
Did Romania switch sides in WW1?
Not exactly. It was formally allied with Germany and Austria-Hungary before 1914, stayed neutral, then joined the Entente in 1916. It signed a separate peace in May 1918, then re-entered the war on 10 November 1918, one day before the Armistice.
What happened to Romania's oil in WW1?
Romanian and British personnel destroyed much of the Ploiești oil infrastructure in late 1916 to deny it to the Germans. The Central Powers restored part of the production, so Romanian oil still helped them during 1917.
Conclusion
Romania in World War 1 is a story of a late entry, a disastrous 1916 campaign and a recovery that ended with Greater Romania. It shows that oil, supply lines and timing decide wars as much as soldiers do.
Want to test these decisions yourself? Start a match in Frontkrieg: a new game begins every day, it is free with no pay-to-win, and more history and strategy articles are in our blog.