Although his parents separated shortly after the marriage, just before his birth, Ionel Brătianu recognized him as a legitimate son and took care to supervise the intellectual formation of the young George.
In 1916 he got his bachelor's degree in Iași, and in the summer of the same year he visited for the first time the historian Nicolae Iorga, in Vălenii de Munte.
Nicolae Iorga was the one who published his first study "A Moldovan army three centuries ago" (O oaste moldovenească acum trei veacuri), in "Revista istorică", representing the historiographical debut of the young Gheorghe I. Brătianu, aged 16.
After Romania joined World War I, on 15 August 1916, Gheorghe I. Brătianu, aged 18, was enrolled voluntarily and incorporated into the 2nd Artillery Regiment.
Between 10 October 1916 - 31 March 1917, he attended the school of artillery reserve officers in Iași, and on 1 June 1917, he was promoted to the rank of lieutenant.
Attracted by history, he abandoned his legal career and enrolled at the Sorbonne University in Paris, where he attended the courses of prestigious historians, such as Ferdinand Lot and Charles Diehl, and got a degree in letters in 1921.
Along with Gheorghe I. Brătianu, a series of prominent personalities of the Romanian interwar culture and politics left NLP, such as Ștefan Ciobanu, Constantin C. Giurescu, Petre P. Panaitescu, Simion Mehedinți, Artur Văitoianu, Mihai Antonescu, etc.
[7] King Carol II notes in his diary that the historian Gheorghe I. Brătianu was "the great apostle of the agreement with Germany".
Nicolae Titulescu, who supposedly had already promised his French and Czechoslovak partners that they had already concluded mutual assistance treaties with the Soviet Union in the event of a European conflict, that he would also conclude a similar treaty, which would have allowed Soviet troops to pass through Romania to "support" France and Czechoslovakia against Germany, also allegedly hid the government's Petrescu-Comnen report.
[9] A month later, on 20 November, informed by Mihail Sturdza about this fact, Gheorghe I. Brătianu, travels to Berlin , where Hermann Göring and Adolf Hitler, with whom he had conversations, but also baron Konstantin von Neurath, the foreign minister Nazi, supposedly confirms the offer made to Romania.
[10] Nicolae Titulescu's "Combinations" were the subject of several interpellations in parliament by Gheorghe I. Brătianu, who was called a fascist leader by the newspaper "Pravda" on 15 December 1936.
When I criticized three months ago the issue of commitments made by the Romanian Government for the possible transit on its territory of Soviet military formations and war materials, I was opposed from the ministerial bench by the most categorical denials, accompanied by the most insulting qualifications.
If we add to these words the assertions of total identities of views on all issues [...] the question is logical: Where will the "East" send our people and weapons and whether the Pact of Military Assistance concluded between Czechoslovakia and the USSR includes obligations of this nature for Romania?
33 569 of 18 June 1936)[citation needed] A year earlier, on 5 October and 26 November 1935, Gheorghe I. Brătianu, in his speeches in Parliament warned about the danger of Soviet troops entering Romania, as well as the impossibility of forcing them to leave Romanian territory, as long as the Soviet Union he had claims on Bessarabia,[11][12] claiming that opening borders means in fact an invitation to the Bolsheviks in the country.
At the elections of December 1937, the last multi-party elections in interwar Romania, he signed the non-electoral pact with Iuliu Maniu (NPP) and Corneliu Zelea Codreanu, who represented the fascist Iron Guard, against the government led by Gheorghe Tătărescu, NLP prime minister, but without the support of the elders of the party led by Dinu Brătianu.
[15] After the coup d'état of 6 September, when King Carol II was dethroned and determined to go into exile by General Ion Antonescu, he will be asked by the latter to participate in the government, in a tripartite formula, together with the Legionnaire movement.
Horia Sima agreed, but with the condition not to request the ministries targeted by the legionaries, internal, external, education and religious affairs.
[16] At the beginning of Romania's military operations in the Second World War, on 22 June 1941, Gheorghe I. Brătianu was mobilized in the 7th Infantry Division, with the rank of reserve captain, until 12 July 1941.