Beyond the differences in national situations, “supreme command” can be defined as the actual exercise of military command over all of a state’s armed forces, or over those positioned at a front or deployed in a theatre of operations. The holder of the position often held the title of commander-in-chief or supreme commander, especially during the twentieth century. For instance in 1951-1952, Dwight David Eisenhower was the Supreme Allied Commander in charge of NATO forces in Europe. The position is sometimes disguised under other names. Napoleon Bonaparte exercised supreme command over the Army of Italy with the title “general-in-chief,” Franco took the title of “generalissimo” in September 1936, and Stalin became “supreme commander” in September 1941. It is important to distinguish between the actual supreme command of troops and the nominal authority without this actual command. In the context of the constitution of the French Third Republic, the head of state had “the armed forces at his disposal,” but in no way exercised actual command over mobilized troops. On the contrary, since 1958 the head of state—who is the “head of the armed forces” according to the Constitution—exercises genuine authority over the armed forces and is the only one to have the nuclear weapon at his disposal. For these tasks, he is assisted by a dedicated military staff. The occupier of the post stands out from other military commanders by the scope of the troops placed under his authority, as well as the objective pursued, which is of the order of general strategy.

Usually exercised on a national level, especially during times of peace, the position of commander-in-chief can give its holder authority over the armed forces of several states. This was the case for General Foch, who in March 1918 was entrusted with “coordinating the action of Allied armies on the Western front,” and who was appointed “commander-in-chief of Allied forces” in April of the same year. In fact, attribution of the title and functions of commander-in-chief does not necessarily imply the exercise of exclusive authority over the troops available. For example, in the spring and summer of 1918, General Pétain, who was the commander-in-chief of the French army on the primary (Northeastern) front, was placed under the authority of General Foch. In 1940, General Georges, who was the commander-in-chief of French armed forces on the Northeastern front, had to follow the strategic orders of General Gamelin, who was the commander-in-chief of all land forces. The supreme command over a theatre of operations or a military front can nevertheless give its holder genuine independence in decision-making. This is how General Bonaparte, who was the general-in-chief of the army of Italy, conducted the first Italian campaign as he saw fit.

At the beginning of the modern era, supreme command over all national troops—or over the primary front where they were engaged—was in principle exclusive to the monarch, who according to Frederick II had to be “the head of his army as of his residence.” The “Roi-Connétable” [King-Constable], to use Pierre Barral’s expression, personally oversaw land troops, as command over naval forces was delegated to admirals. This arrangement remained in effect in most European monarchies until the mid-twentieth century, even constitutional ones. For instance, Napoleon personally commanded the troops engaged in the primary theatre of operations, from Marengo (1800) to Waterloo (1815). This was also the case for the King of Prussia, who from August 1870 personally commanded the troops positioned against France. During the first months of The Great War, Emperor William II officially took on the high command of the Reich’s armed forces, and exercised real authority over the chief of staff, General Helmuth von Moltke the Younger. Albert I, and later his son Leopold III, were supreme commanders of the Belgian army in 1914-1918 and 1939-1940, while placing themselves under inter-Allied authority.

Nevertheless, beginning with the early modern period there was an evolution towards granting the actual exercise of supreme command to a figure distinct from the sovereign. In 1693, Louis XIV left his troops in Northern France in the middle of a campaign, entrusting command to the Marshall of Luxembourg. During the wars of the French Revolution and the Empire, the Austrian troops confronting French armed forces were rarely commanded by the Emperor Francis in person, who preferred delegating this task to his brothers, the Archdukes Jean-Baptiste and especially Charles-Louis (fig. 1). During the nineteenth and twentieth centuries, the distinction became even clearer between the political management of the state and supreme command over the military, which was entrusted to an officer-general who was a military professional. Only certain monarchs, such as Napoleon III and Nicholas II, along with totalitarian heads of state, did not adhere to this evolution. In order to increase their prestige, they often seized the supreme command before a war, or after a war had started badly .

While during the modern period political power tended to detach itself from military command, in certain circumstances the general-officers in charge of the supreme command stepped into the political and governmental sphere. This position indeed bestowed an aura—albeit an often irrational one— enabling the holder to play a central political role, notably in cases of international conflict, or as part of conflicts within authoritarian regimes. The quasi-dictatorship exercised by the Generals Hindenburg and Ludendorff in the Reich from August 1916 onward attests to this trend. From 1926 to 1935, Marshall Pilsudski, a hero of independence, held a tight grip over Poland’s internal and foreign policy. He was the minister of military affairs and inspector general of the armed forces, and was also designated as commander-in-chief in case of war. From 1920 to 1944, the Regency exercised in Hungary by the former commander-in-chief of the Austro-Hungarian fleet Miklos Horthy (fig. 2), demonstrates that defeat did not wither the laurels of this “admiral without a fleet” or “regent of a kingless kingdom,” who in effect ruled as the actual Hungarian head of state from 1920 to 1944. Democratic regimes sometimes allowed past or present supreme commanders to rise to power. On September 23, 1938, amid an international crisis, the president of the Czech Republic entrusted management of the government to the inspector general of the army, Jan Syrovy. The prestige as former commander-in-chief of the French army played an essential role in Philippe Pétain’s rise to power in June 1940.

However, in post-1945 Europe, which has been marked by the domination of democracies and the relegation of open-armed conflict to the periphery of the continent or beyond, the supreme command of armed forces is no longer a central aspect of the functioning of states and societies. After the end of the Cold War, sharp reductions in the format of armies and the almost complete disappearance of conscription in Europe have strengthened this evolution, even though the title of “commander-in-chief” remains in use, notably in connection with the hierarchy of the integrated forces of the Atlantic Alliance (fig. 3). Still, the exercise of supreme command remains an essential tool in analyzing and comprehending the Europe of large battalions and “nations in arms,” from the “guerre en dentelles” [war in lace] to the two world wars.