In 1859 Wallachia and Moldavia, while nominally under Turkish sovereignty, joined to form a united and autonomous Rumanian state. After studying law and political science in Paris, Marghiloman returned to Rumania to begin an important career in that country's Conservative party in 1884.
At the outbreak of the war in 1914 Marghiloman was the leader of his party. The Conservatives soon split over whether to support the Entente or the Central Powers. To Marghiloman, an outspoken advocate of a tie with Germany, the best to be expected in a Francophile country was continued neutrality. He advocated this policy at the August 3, 1914, crown council at Sinaia, which decisively rejected implementing Rumania's secret defensive treaty with the Triple Alliance. As irredentist and pro-Entente fever rose in September, Marghiloman aligned himself with King Carol and Premier Bratianu to urge continued neutrality. Far from being a ready collaborator with the Central Powers, Marghiloman pushed Carol to use Austria's plight to gain better treatment for Rumanians within the Austro-Hungarian empire. Bratianu apparently thought he could safeguard Rumania's interest, assuming victory for the Entente. On the other hand, as he told Marghiloman, the Conservative leader could take over and serve the same purpose in the event the Central Powers prevailed.
Marghiloman saw his party split in May 1915: proEntente figures like Filipescu demanded Rumania follow Italy's lead into the war. The German and Austrian victories of the following months raised rumors Marghiloman might replace Bratianu a change the Central Powers urged but the premier continued to dominate both Rumania's monarch and parliament. So long as Bratianu felt the time was not ripe for war, Rumania retained a friendly neutral stance toward the Entente, Marghiloman's will notwithstanding.
The victorious Allied push in the Balkans (September/October 1918) made all of this futile. By early November the Germans had begun to evacuate their troops from Rumania. Alert diplomacy by the United States raised hopes in Bucharest for territorial gains in return for renewing hostilities. Bratianu persuaded the king that Marghiloman had served his purpose, and Ferdinand installed a new government on November 6.
Marghiloman remained an active figure in Rumanian politics during the years following the war, but he and his Conservative party were fatally compromised by their actions during the German occupation. Marghiloman justified his conduct by pointing to the annexation of Bessarabia, as well as his country's success in maintaining its dynasty and even part of its army in the aftermath of military disaster. Seton-Watson added a historian's endorsement to Marghiloman's self-justification, calling him Rumania's "one man in occupied territory who showed a gleam of statesmanship" in helping to save the dynasty, and overall a patriot who served his country well.
Marghiloman died at his birthplace, Buzau, on May 10, 1925. His five volumes of memoirs, Notice Politice, 1897-1924, appeared in Rumanian shortly after his death.