Organization of a nation's armed forces for active military service in time of war or other national emergency. It includes recruiting and training, building military bases and training camps, and procuring and distributing weapons, ammunition, uniforms, equipment, and supplies. Full mobilization involves summoning all of a nation's resources to support the military effort; for example, civilians may gather raw materials needed by the military, conserve scarce resources such as gasoline for military use, or sell war bonds to fund the war effort.
Learn more about mobilization with a free trial on Britannica.com.
Mobilization is the act of assembling and making both troops and supplies ready for war. The word mobilization was first used, in a military context, in order to describe the preparation of the Prussian army during the 1850s and 1860s. Mobilization theories and techniques have continuously changed since then. Notably, before World War I and World War II, several countries developed intricate plans to achieve a fast and effective mobilization in case of war. The opposite of mobilization is demobilization.
Mobilization can be complete, or partial, in which case only a part of the reserves is called up.
Mobilization became an issue with the introduction of conscription, and the introduction of the railways in the 19th Century. Mobilization institutionalized the mass levy of forces that was first introduced during the French Revolution, and that had changed the character of war. A number of technological and societal changes promoted the move towards a more organized way of assembling armies. These included the telegraph, which allowed rapid spreading of orders, the railways, which allowed rapid concentration of troops, and conscription, which provided a trained reserve of soldiers available in the case of war.
Intricate plans for mobilization contributed greatly to the beginning of World War I, since in 1914, under the laws and customs of warfare then observed (not to mention the desire to avoid compromising national security), general mobilization of one nation's military forces was invariably considered an act of war by that country's likely enemies. As the proverb claims, no army has ever mobilized without going to war.
In 1914, the United Kingdom was the only European Great Power without conscription. The other Great Powers (Austria-Hungary, France, Germany and Russia) all relied on compulsory military service to supply each of their armies with the millions of men they believed they would need to win a major war. France enacted the “Three Year Law” (1913) to extend the service of conscripted soldiers to match the size of the German army, as the French population of 40 million was smaller than the German population of 60 million people. The British and the Germans also started a race to build up a stronger navy, sparked by the German enactment of the Second Naval Law. Each of the Great Powers could only afford to keep a fraction of these men in uniform during peacetime, the rest were reservists with limited opportunities to train. Maneuvering formations of millions of men with limited military training required intricate plans which left no room for error, confusion or discretion after mobilization commenced. These plans were prepared under the assumption of worst-case scenarios.
For example, German military leaders did not plan to mobilize for war with Russia whilst assuming that France would not come to her ally's aid, or vice-versa. The Schlieffen Plan therefore dictated not only mobilization against both powers, but also the order of attack—France would be attacked first regardless of the diplomatic circumstances. To bypass the fortified Franco-German frontier, the German forces were to be ordered to march through Belgium. Whether or not Russia had committed the first provocation, the German plan agreed to by Emperor William II called for the attack on Russia to take place only after France was defeated.
Similarly, the Russian STAVKA's war planning assumed that war against either Austria-Hungary or Germany would mean war against the other power. Although the plan allowed flexibility as to whether the main effort would be made against Germany or Austria-Hungary, in either case units would be mobilized on the frontiers of both Powers. On July 28, 1914, Tsar Nicholas II of Russia (William's cousin) ordered partial mobilization against Austria-Hungary only. While war with Austria-Hungary seemed inevitable, Nicholas engaged in a personal dialogue with the German Emperor in an attempt to avoid war with Germany. However, Nicholas was advised that attempts to improvise a partial mobilization would lead to chaos and probable defeat if, as pessimists on the Russian side expected, no amount of diplomacy could convince the Germans to refrain from attacking Russia whilst she was engaged with Germany's ally. On July 29, 1914, the Tsar ordered full mobilization. In response, Germany declared war on Russia.
Germany mobilized under von Moltke the Younger's revised version of the Schlieffen Plan, which assumed a two-front war with Russia and France. Like Russia, Germany decided to follow its two-front plans despite the one-front war. Germany declared war on France on August 3, 1914, one day after issuing an ultimatum to Belgium demanding the right of German troops to pass through as part of the planned pincer action of the military. Finally, Britain declared war on Germany for violating Belgian neutrality.
Thus the entangling alliances of the Triple Alliance and the Triple Entente directed the intricate plans for mobilization. This brought all of the Great Powers of Europe into the Great War without actually utilizing the provisions of either alliance.
The mobilization was like a holiday for many of the inexperienced soldiers; for example, some Germans wore flowers in the muzzles of their rifles as they marched. Trains brought soldiers to the front lines of battle. The Germans timetabled the movements of 11,000 trains as they brought troops across the Rhine River. The French mobilized around 7,000 trains for movement. Horses were also mobilized. The British had 165,000 horses prepared for cavalry, the Austrians 600,000, the Germans 715,000, and the Russians over a million.
Britain's Dominions including Australia, Canada, New Zealand and South Africa were compelled to go to war when Britain did. However, it was largely left up to the individual Dominions to recruit and equip forces for the war effort. Canadian, Australian and New Zealand mobilizations all involved the creation of new field forces for overseas service rather than using the existing regimental structures as a framework. In the case of Canada, the Militia Minister, Sir Sam Hughes, created the Canadian Expeditionary Force from whole cloth by sending telegrams to 226 separate reserve unit commanders asking for volunteers to muster at Valcartier in Quebec. The field force served separately from the Militia (Canada's peace time army); in 1920 the Otter Commission was compelled to sort out which units would perpetuate the units that served in the trenches - the CEF or the prewar Militia. A unique solution of perpetuations was instituted, and mobilization during the Second World War did not repeat Sir Sam Hughes' model, which has been described by historians as being more closely akin to ancient Scottish clans assembling for battle than a modern, industrialized nation preparing for war.
"Colonials" served under British command, although perhaps owing to the limited autonomy granted to the Dominions regarding their respective mobilizations the Dominions eventually compelled the British government to overrule the objections of some British commanders and allow the Dominion forces to serve together instead of being distributed piecemeal amongst the various British divisions. The "colonials" would go on to be acknowledged by both the British and German high commands as being elite British units.
On May 23, Italy entered World War I on the Allied side. Despite being one of the weakest of the Allied powers, the Italians soon managed to populate its army from 560 to 693 infantry battalions in 1916; the army had grown in size from a million to one and a half million soldiers. On August 17, 1916, Romania entered the war on the Allied side, mobilizing an army of 23 divisions. Romania was quickly defeated however by the Germans and Austrians.
The production of supplies gradually increased throughout the war. In Russia, the expansion of industry allowed a 2,000 percent increase in the production of artillery shells - by November 1915, over 1,512,000 artillery shells were being produced per month. In France, a massive mobilization by the female population to work in factories allowed the rate of shell production to reach 100,000 shells a day by 1915.
Both sides also began drawing on larger amounts of soldiers. The British Secretary of State for War, Lord Kitchener, appealed for hundreds of thousands of soldiers, which was met with an enthusiastic response. 30 new British divisions were created. The response by volunteers allowed the British to put off the introduction of conscription until 1916. New Zealand followed suit, with Canada also eventually introducing conscription.
On April 6, 1917, the United States entered the war on the Allied side. At the entrance, the U.S. only could mobilize its army of 107,641 soldiers, ranked only seventeenth in size worldwide at the time. The United States Navy quickly mobilized, adding 5 dreadnoughts to the Allied navy. However, conscription quickly ensued. By March 1918, 318,000 U.S. soldiers had been mobilized to France. Eventually, a force of 3 million U.S. soldiers joined in the war effort.
Canada actually carried out a partial mobilization on 25 August 1939. in anticipation of the growing diplomatic crisis. On September 1 1939, the Canadian Active Service Force (a corps-sized force of two divisions) was mobilized despite war not being declared by Canada until September 10 1939. Only one division went overseas in Dec 1939, and the government hoped to follow a "limited liability" war policy. When France was invaded in May 1940, the Canadian government realized that would not be possible and mobilized three additional divisions, beginning their overseas employment in Aug 1940 with the dispatch of the 2nd Canadian Division (some units of which were deployed to Iceland and Newfoundland for garrison duty before moving to the UK). Canada also enacted the National Resources Mobilization Act in 1940, which among other things compelled men to serve in the military, though conscripts mobilized under the NRMA did not serve overseas until 1944. Conscripts did, however, serve in the Aleutian Islands in 1943 though the anticipated Japanese defence never materialized due to the evacuation of the enemy garrison before the landings. Service in the Aleutians was not considered "overseas" as technically the islands were part of North America.