He graduated first from his class of 1884 at the Saint-Cyr military academy.
Commissioned as an infantry officer after completing St. Cyr in 1884, he served with distinction in several capacities before August 1914. Guillaumat fought in twelve colonial campaigns including the Boxer Rebellion. The rising young officer taught at the War College in 1907, and, two years later, commanded the La Flèche School for the sons of French soldiers. He directed the infantry office at the War Ministry, and, for a brief period in mid-1914, was chef de cabinet to the minister of war.
The course of World War I brought Guillaumat additional opportunities to add to his already bright reputation in the officer corps. He led a division at the battle of the Marne, rose to corps command in 1915, and was clearly marked to go higher still. At the close of 1916, in the reshuffling of high level posts that followed the ouster of General Joffre as commander in chief, Guillaumat received the Second Army. In the precarious conditions of mid-1917, he convinced General Pétain, the new French generalissimo, that the Second Army could stage a successful offensive at Verdun. Guillaumat's August assault on Mort 'Homme and Hill 304 was the first of Pétain's carefully managed offensives designed to restore the confidence of the badly shaken French forces. A failure would have had incalculable consequences for the entire western front, but Guillaumat did not fail. Using a massive artillery preparation and a two-day advance, he gave Pétain precisely the victory the commander in chief needed.
As reward, Pétain named Guillaumat to lead the Army of the Orient in Macedonia. Guillaumat left in December 1917 to reorder the Balkan tangle created by his cashiered predecessor, General Sarrail. A proven combat leader, well regarded in the National Assembly but free of embarrassing close links to any political party, Guillaumat turned out to be the ideal man for the task. He moved at once to restore good relations with France's allies on the multinational Balkan front and began to prepare for a vigorous offensive two areas in which Sarrail had been notably deficient. No troops were available from the western front, of course, but Guillaumat had a solution there as well. He welcomed several Greek divisions into his force; Prime Minister Venizelos had brought Greece into the war in July 1917. Guillaumat bolstered the morale of the untested Greek units by encouraging their assault on the Bulgar stronghold at Skra di Legen (May 1918), a success upon which the Greeks prided themselves for the remainder of the war.
The crisis on the western front led Pétain to recall Guillaumat; he was replaced by General Franchet d'Esperey, whose brilliant career had received a potentially fatal setback during the Second Battle of the Marne. Guillaumat took over as military governor of Paris and served as the French representative to the Supreme War Council at Versailles. But he had a lasting interest in the Balkans. With most eyes turned to the crisis on the western front, Guillaumat became d'Esperey's leading supporter in the highest councils at home on the possibility of a fall offensive in the Balkans. He won over the Supreme War Council in July; in a personal visit to London (September 1918), the enthusiastic Guillaumat convinced the British government to back a major effort in Macedonia. Having thus set the stage for d'Esperey's great march from Macedonia to Hungary, Guillaumat spent the final weeks of the war in the field at the head of the Fifth Army driving into the Ardennes.
Guillaumat's wartime exploits made him a major figure in the postwar army: member of the Supreme War Council, army inspector general, and commander of French occupation forces in Germany (1924-1930). In 1926 he served briefly as minister of war under Aristide Briand. He died at Nantes, in June 1940.
General Guillaumat was a practising Catholic and an admirer of Frédéric Bastiat.
Adolphe Guillaumat married Louise Bibent from Toulouse on July 17, 1906 and had two sons: Louis, who became an Ophthalmologist, and Pierre, who became a Civil servant and served as a Minister of the Armies of General De Gaulle after the latter's return to power from June 1, 1958 to February 5, 1960.