Military strategy
His theory defied popular military thinking of the time, which was strongly in favour of victory in battle, yet World War I would soon demonstrate the flaws of a mindless "strategy of annihilation".
At a time when industrialisation was rapidly changing naval technology, one American strategist, Alfred Thayer Mahan, almost single-handedly brought the field of naval strategy up to date. Influenced by Jomini's principles of strategy, he saw that in the coming wars, where economic strategy could be as important as military strategy, control of the sea granted the power to control the trade and resources needed to wage war. Mahan pushed the concept of the "big navy" and an expansionist view where defence was achieved by controlling the sea approaches rather than fortifying the coast. His theories contributed to the naval arms race between 1898 and 1914.

World War I: At the start of World War I strategy was dominated by the offensive thinking that had been in vogue since 1870, despite the more recent experiences of the Second Boer War (1899–1902) and Russo-Japanese War (1904–05), where the machine gun demonstrated its defensive capabilities. By the end of 1914, the Western Front was a stalemate and all ability to maneuver strategically was lost. The combatants resorted to a "strategy of attrition". The German battle at Verdun, the British on the Somme and at Passchendaele were among the first wide-scale battles intended to wear down the enemy. Attrition was time-consuming so the duration of World War I battles often stretched to weeks and months. The problem with attrition was that the use of fortified defenses in depth generally required a ratio of ten attackers to one defender, or a level of artillery support which was simply not feasible until late 1917, for any reasonable chance of victory. The ability of the defender to move troops using interior lines prevented the possibility of fully exploiting any breakthrough with the level of technology then attainable.
Perhaps the most controversial aspect of strategy in World War I was the difference among the British between the "Western" viewpoint (held by Field Marshal Haig) and the "Eastern"; the former being that all effort should be directed against the German Army, the latter that more useful work could be done by attacking Germany's allies. The term "knocking away the props" was used, perhaps as a consequence of the fact that all of Germany's allies lay south of (i.e., "beneath") it on the map. Proponents of the Western viewpoint make the point that Germany's allies were more than once rescued from disaster or rendered capable of holding their own or making substantial gains by the provision of German troops, arms or military advisers, whereas those allies did not at any time provide a similar function for Germany. That is, it was Germany which was the prop, and its allies (particularly Bulgaria and Austria-Hungary) did not suffer significant reverses until Germany's ability to come to their aid was grossly impaired.
On other fronts, there was still room for the use of strategy of maneuver. The Germans executed a perfect battle of annihilation against the Russians at the Battle of Tannenberg. In 1915 Britain and France launched the well-intentioned but poorly conceived and ultimately fruitless Dardanelles Campaign, combining naval power and an amphibious landing, in an effort to aid their Russian ally and knock the Ottoman Empire out of the war. The Palestine campaign was dominated by cavalry, which flourished in the local terrain, and the British achieved two breakthrough victories at Gaza (1917) and Megiddo (1918). Colonel T. E. Lawrence and other British officers led Arab irregulars on a guerrilla campaign against the Ottomans, using strategy and tactics developed during the Boer Wars.
World War I saw armies on a scale never before experienced. The British, who had always relied on a strong navy and a small regular army, were forced to undertake a rapid expansion of the army. This outpaced the rate of training of generals and staff officers able to handle such a mammoth force, and overwhelmed the ability of British industry to equip it with the necessary weapons and adequate high-quality munitions until late in the war. Technological advances also had a huge influence on strategy: aerial reconnaissance, artillery techniques, poison gas, the automobile and tank (though the latter was, even at the end of the war, still in its infancy), telephone and radio telegraphy.
More so than in previous wars, military strategy in World War I was directed by the grand strategy of a coalition of nations; the Entente on one side and the Central Powers on the other. Society and economy were mobilized for total war. Attacks on the enemy's economy included Britain's use of a naval blockade and Germany employing submarine warfare against merchant shipping.
Unity of command became a question when the various nation states began coordinating assaults and defenses. Under the pressure of horrendously destructive German attacks beginning on March 21, 1918, the Entente eventually settled under Field Marshal Ferdinand Foch. The Germans generally led the Central Powers, though German authority diminished and lines of command became confused at the end of the war.
World War I strategy was dominated by the "spirit of the offensive", where generals resorted almost to mysticism in terms of a soldier's personal "attitude" in order to break the stalemate; this led to nothing but bloody slaughter as troops in close ranks charged machine guns. Each side developed an alternate thesis. The British under Winston Churchill developed tank warfare, with which they eventually won the war. The Germans developed a "doctrine of autonomy", the forerunner of both blitzkrieg and modern infantry tactics, using groups of stormtroopers, who would advance in small mutually covering groups from cover to cover with "autonomy" to exploit any weakness they discovered in enemy defenses. Almost all the blitzkrieg commanders of World War II, particularly Erwin Rommel, were stormtroopers in World War I. After the Treaty of Brest-Litovsk, Germany launched and almost succeeded in a final offensive. However, the new tactics of autonomy revealed a weakness in terms of overall coordination and direction. The March offensive, intended to drive a wedge between the French and British armies, turn on the latter and destroy it, lost direction and became driven by its territorial gains, its original purpose neglected.
World War I ended when the ability of the German army to fight became so diminished that Germany asked for peace conditions. The German military, exhausted by the efforts of the March offensives and dispirited by their failure, was first seriously defeated during the Battle of Amiens (8–11 August 1918) and the German homefront entered general revolt over a lack of food and destruction of the economy. Victory for the Entente was almost assured by that point, and the fact of Germany's military impotence was driven home in the following hundred days. In this time, the Entente reversed the gains the Germans had made in the first part of the year, and the British Army (spearheaded by the Canadians and Australians) finally broke the Hindenburg defensive system.
Though his methods are questioned, Britain's Field Marshal Haig was ultimately proved correct in his grand strategic vision: "We cannot hope to win until we have defeated the German Army." By the end of the war, the best German troops were dead and the remainder were under continuous pressure on all parts of the Western Front, a consequence in part of an almost endless supply of fresh American reinforcements (which the Germans were unable to match) and in part of industry at last supplying the weakened Entente armies with the firepower to replace the men they lacked (while Germany wanted for all sorts of materials thanks to the naval blockade). Interior lines thus became meaningless as Germany had nothing more to offer its allies. The props eventually fell, but only because they were themselves no longer supported.
The role of the tank in World War I strategy is often poorly understood. Its supporters saw it as the weapon of victory, and many observers since have accused the high commands (especially the British) of shortsightedness in this matter, particularly in view of what tanks have achieved since. Nevertheless, the World War I tank's limitations, imposed by the limits of contemporary engineering technology, have to be borne in mind. They were slow (men could run, and frequently walk, faster); vulnerable (to artillery) due to their size, clumsiness and inability to carry armour against anything but rifle and machine gun ammunition; extremely uncomfortable (conditions inside them often incapacitating crews with engine fumes and heat, and driving some mad with noise); and often despicably unreliable (frequently failing to make it to their targets due to engine or track failures). This was the factor behind the seemingly mindless retention of large bodies of cavalry, which even in 1918, with armies incompletely mechanised, were still the only armed force capable of moving significantly faster than an infantryman on foot. It was not until the relevant technology (in engineering and communications) matured between the wars that the tank and the airplane could be forged into the co-ordinated force needed to truly restore manoeuvre to warfare.

Inter war: In the years following World War I, two of the technologies that had been introduced during that conflict, the aircraft and the tank, became the subject of strategic study.
The leading theorist of air power was Italian general Giulio Douhet, who believed that future wars would be won or lost in the air. The air force would carry the offensive, and the role of the ground forces would be defensive only. Douhet's doctrine of strategic bombing meant striking at the enemy's heartland—his cities, industry and communications.