The main principles of his premiership were to create Allied unity, and to maintain an allied presence in the Balkans. He always claimed the credit for the idea of the Salonika front to ease the path towards the achievement of France's postwar hegemony in the Eastern Mediterranean by establishing a French presence in Greece to replace that lost in Serbia. He had intervened personally to overcome General Sarrail's initial refusal to accept the command of the Army of the Orient by increasing the effectives over which he would have control; and, by extending Joffre's powers on 2 December 1915 to control of all fronts, he ensured that the generalissimo would have to pay some attention to the Balkans area. As for interallied unity, one of Briand's earliest acts was to propose regular diplomatic meetings between the Allies, along the same lines as the military conferences. After only one month as premier he initiated discussions about the institution of an International Council of War. The first allied war conference took place in Calais in December 1915 (over the Salonika question), to be followed by two more conferences in Paris in March and June 1916. The last mentioned passed the so-called Paris Resolutions in order to strengthen the economic war and to provide for the postwar economic settlement.
It was during Briand's premiership that the Battle of Verdun was fought, and so he had to deal with the parliamentary unrest caused by the near disaster. The first of several secret sessions of the Chamber of Deputies and the Senate took place in June 1916. His hold on the premiership became increasingly shaky thereafter and at the end of 1916 he jettisoned General Joffre in an attempt to stave off criticism of his own handling of the war, promoting the general to Marshal as recompense.
After his resignation just before the Nivelle offensive in 1917, he retired from public life but became embroiled in the so-called Lancken affair. The Baron de Lancken was a German government official in occupied Belgium who was persuaded that peace feelers might be acceptable to the French. Briand agreed to meet Lancken in Switzerland in September 1917, but later pulled out on official advice. Briand's belief that Lancken would be prepared to accept the return of Alsace-Lorraine to France and Lancken's belief that Briand would be flexible about French demands for the return of those same provinces were incompatible. Questions of morale in France in 1917 were highly sensitive, given the mutinies and the strikes, and so Briand did himself no good among parliamentarians by his ill-advised incursion into peace negotiations.
Nonetheless, Briand was awarded the Nobel Peace Prize in 1926 and is the only foreign minister since the sixteenth century to be honoured by a statue bust erected to his memory in the railings of the Quai d'Orsay.
Source: There is a multi-volume biography which is marred by its deferential tone and verbatim quotations of supposedly confidential conversations. It does, however, have the virtue of citing documents which Briand supplied for the purpose from the archives: Georges Suarez Briand : sa vie, son Oeuvre. Avec son Journal et de nombreux documents inedits, 5 vols. (Paris: Plon 1938-41).