Thus, all the armies and navies of Europe faced each other across fortified front lines. The prewar plans had succumbed to the technological surprise of 1914–15: that the withering firepower of machine guns, cartridge rifles, and rapid-fire artillery favoured the defense. Infantry in deep trenches, fronted with mines and barbed wire and backed by artillery, could not be dislodged by frontal attack. Accordingly, military and political leaders spent the war groping for means of breaking the stalemate in the trenches. First, neutrals might be enticed to enter the war, perhaps throwing enough weight into the balance to provide victory. Second, new weapons, tactics, and theatres might break the deadlock or achieve strategic goals elsewhere. Third, more and more men and matériel might be squeezed out of the home economy to tip the balance of forces or wear down the enemy by economic attrition. The first of these means determined much of the diplomatic history of the war. The second stimulated technological developments such as poison gas, tanks, and submarines, as well as the peripheral campaigns of southern Europe and the Middle East. The third determined the evolution of war economies and the character of what came to be called total war.

The first of the European neutrals to join the fray was the Ottoman Empire. Having lost the Balkans before 1914 and fearing partition of their Arab possessions by the Triple Entente, the Young Turks under Enver Paşa looked to Germany, whose military efficiency they admired. Enver led in negotiating a secret German-Ottoman treaty, signed August 2, 1914. But the grand vizier and others in the sultan’s court held back, even after extracting a German loan—tantamount to a bribe—of £5,000,000. The war party then resorted to more extreme measures. The Ottoman fleet, reinforced by two German cruisers, entered the Black Sea in October, bombarded Odessa and the Crimean ports, and sank two Russian ships. The commander then falsified his account to make it appear that the enemy had provoked the action. The outraged Russians declared war on November 1. The Ottoman Empire’s alliance with the Central Powers was a serious blow to the Entente, for it effectively isolated Russia from its Western allies and weakened their hand in the Balkan capitals. The Turks concluded, however, that a Triple Entente victory in the war would lead to the partition of their empire even if they remained neutral (Allied negotiations had already begun to this effect), whereas joining forces with Germany gave them at least a fighting chance to survive and perhaps even win some spoils from Russia. Enver also declared a jihad, or holy war, inciting Muslims to rise up against British and Russian rule in India, Persia, and Central Asia.

Turkish forces deployed along the coasts of the Dardanelles and on the Caucasus frontier with Russia, where severe fighting began in the rugged mountains. Enver, with German encouragement, took the strategic offensive when he ordered 10,000 troops from Syria to attack the Suez Canal in late January 1915. After crossing the Sinai Peninsula the tired soldiers found Indian and Australasian divisions in training, as well as gunboats and other equipment they could not match. The Turks fell back to Palestine and never menaced the canal again.

The vulnerability and value of the Dardanelles in turn attracted the British. When Russia requested a Western assault on Turkey to relieve the pressure in the Caucasus, War Secretary Lord Kitchener and First Lord of the Admiralty Winston Churchill promoted an attack on the Dardanelles. By capturing Constantinople, the British could link up with the Russians, knock Turkey out of the war, and perhaps entice the Balkan states to rally to the Allied cause. The British War Council created an amphibious force of British, Australians, and New Zealanders to capture the heights of the Gallipoli Peninsula. On April 25 the ANZAC (Australian and New Zealand Army Corps) forces went ashore, but their assaults on the heights of Sari Bair were turned back through the charismatic leadership of the young Turkish officer Mustafa Kemal. A sweltering, bloody deadlock dragged on into the summer. Five more divisions and another amphibious landing, at Suvla Bay in August, failed to take the rugged heights in the face of human wave counterattacks by the Turks. Cabinet opinion gradually turned against the campaign, and the Allied force of 83,000 was evacuated—a dangerous operation conducted with great skill—in January 1916. The Turks had lost some 300,000 men, the Allies about 250,000 to battle and disease. Gallipoli was, in Clement Attlee’s words, “the one strategic idea of the war.” Its failure, through bad leadership, planning, and luck, condemned the Allies to seek a decision in bloody battles of attrition on the Western Front.

The other peripheral front that enticed Allied strategists was Austria’s border with Italy. Though a member of the Triple Alliance, the Rome government maintained on August 3, 1914, that it was not bound to fight since Austria had not been attacked nor had it consulted with Italy as the treaty required. Prime Minister Antonio Salandra, a nationalist dedicated to the Irredentists’ goal of recovery of Trentino and Trieste from Austria, announced that Italy would be informed by sacro egoismo. This, he explained, was a mystical rather than cynical concept, but it set off seven months of haggling over what the Allies would offer Italy to enter the war, and what the Central Powers would offer for neutrality. Some considerations were objective: Italy’s 4,160 miles of coastline made defense against the Anglo-French fleet virtually impossible; any gains extorted from the Central Powers for neutrality would hardly be secure should those powers win the war; and neutrality was incompatible with Italy’s tenuous claim to be a great power. What was more, all the Central Powers could offer was Trentino, and even that promise had to be forced from Vienna by German pressure.

After a clumsy intervention by the Russian foreign minister, Sazonov, in which he tried to secure Italy’s help and still protect Serbian interests on the Dalmatian coast, negotiations moved to London. Berlin dispatched ex-chancellor Bülow and Roman Catholic statesman Matthias Erzberger to Rome to plead for the Central Powers. On April 26, the day after the first Gallipoli landing, the Treaty of London committed Italy to enter the war against Austria-Hungary within a month. In return the Allies promised Italy Trentino, part of South Tirol, Trieste, a third of Dalmatia (at the expense of Serbian ambitions), a mandate over Albania, a portion of German East Africa, all of Libya, a part of Asia Minor, and a 1,250,000,000-lira war chest from Britain. Still, a month of crisis followed in Rome as journalists like Gabriele D’Annunzio and Benito Mussolini stoked war fever and parliamentary power-broker Giovanni Giolitti (backed by Bülow) maneuvered for peace and parecchio—the “much” that might be obtained from Austria without lifting a rifle. After a cabinet crisis Salandra returned to power to declare war on Austria-Hungary on May 23, 1915 (though Italy did not declare war on Germany until August 1916).

General Luigi Cadorna’s war plan called for a strategic defense in the mountainous Trentino while half the Italian army concentrated for attack along the Isonzo River to the south. In June 1915 he launched the first of 11 battles of the Isonzo, wasting some 250,000 men against the rocky parapets and spirited Austrian defenders. The southern front became another deadlock, while Italy’s weak finances and industry would only make her a continuing drain on Anglo-French resources.

After Turkey and Italy, attention turned to the neutral Balkan states. The entry of the Balkan states on the side of the Central Powers would doom Serbia and open direct communications between Germany and Turkey. Balkan participation on the Allied side would isolate Turkey and complete the encirclement of Austria-Hungary. The Central Powers had the upper hand in Bulgaria, still smarting from its defeat in the Second Balkan War and allied with Turkey as of August 2, 1914. The Allies had little to offer Bulgaria except bribes, especially after their failure at Gallipoli. German offers proved irresistible: Macedonia (from Serbia) and parts of the Dobruja and Thrace should Romania and Greece intervene. Bulgaria joined the Central Powers on September 6, 1915. In Romania the Allies had the upper hand despite a treaty, renewed in 1913, binding Bucharest and its Hohenzollern dynasty to the Triple Alliance. Romania’s main ambition was to annex Transylvania, a Habsburg province populated largely by Romanians, but Prime Minister Ionel Brătianu determined to stay neutral and observe the fortunes of war.

In 1915 those fortunes appeared to favour the Central Powers on the Turkish, Italian, Serbian, and Russian fronts. The Russian front collapsed in the face of a German offensive in May, allowing the Central Powers to reoccupy Galicia, Lithuania, and Courland in the north. In July the Germans resumed the drive and threatened to pincer the entire Russian army in Poland. Warsaw fell on August 5 and Brest-Litovsk on the 26th, whereupon the German armies outran their supplies and halted the drive on a line stretching from Riga on the Baltic to Czernowitz on the Romanian border. Russian losses were apocalyptic: more than a million men captured and at least as many killed and wounded in 1915. Technical inferiority, shortage of munitions, and poor tactics led to terrible wastage of men in the attack and lack of mobility on the defense. The inadequacy of the Russian state and economy in modern war now stood revealed. Desertions increased and morale plummeted. On September 5, Tsar Nicholas himself took over supreme command, a chivalrous move but one that would identify the crown with future disasters.

In 1916 German strategists again turned west with the expressed intention of bleeding France white and breaking her army’s spirit. The object of attack was to be the fortress of Verdun, and the plan called for the substitution of ordnance for manpower as much as possible, thereby using Germany’s industrial might to kill Frenchmen in the most efficient way. The assault began on February 21, following an avalanche of shells and poison gas, and continued without interruption for five months. France’s civilian and military leadership turned Verdun into a national symbol of resistance, symbolized by General Philippe Pétain’s famous order of the day: “Ils ne passeront pas!” Verdun was the most intensive battle in history and cost France and Germany more than 300,000 men each.

In December 1915 an Allied conference at Chantilly had decided to coordinate simultaneous attacks on all fronts. Given Verdun, responsibility for the Western assault fell to the British. After elaborate preparation and a week of bombardment the cream of “Kitchener’s New Army” went over the top on July 1, 1916, and strode in formation toward the German lines. By mid-November the Somme offensive had gained about six and a half miles across a 30-mile front at the cost of 420,000 Britons, 194,000 Frenchmen, and 440,000 Germans.

On the Eastern Front in 1916 the Russian command dutifully took up the offensive to relieve the pressure on Verdun and in coordination with the push on the Somme. But failures in leadership and supply, poor intelligence and tactics again thwarted the courage of Russia’s peasant-soldiers, 100,000 of whom were lost in a March attack that achieved nothing. The last gasp of the tsarist army followed in June. Russian attacks at Lutsk, Buchach, and Czernowitz beginning June 4 achieved total surprise, captured 200,000 men, and overran Bukovina by the end of the month. This apparent revival of Russia’s fortunes prompted the Romanians, finally, to declare war on Austria-Hungary on August 27, 1916. Half the Romanian army—12 divisions—joined the offensive and advanced into Transylvania, expecting to deal the final blow to staggering Austria-Hungary. Instead, Germany, Turkey, and Bulgaria promptly declared war on Romania. The Romanians held out for a month against a German-Austrian-Bulgarian attack at the Vulcan and Szurduk (Surduc) passes, but the Central Powers broke through and captured Bucharest on December 6. The Romanian gambit ended in disaster as the Germans acquired their oil and wheat and the Russians inherited an additional 300 miles of frontline. Meanwhile, the Russian offensive degenerated into frontal assaults and closed in August. Russia had lost 500,000 men—the last trained reserves of the tsarist army.

By the end of 1916 what may be called the traditional phase of the war had run its course. Despite ever greater expenditures of men and matériel and the accession of neutral powers to one side or the other, victory remained elusive. Henceforth the coalitions would rely all the more on breaking the internal cohesion of the enemy or on calling forth global forces to tip the balance. The resort to revolution, especially in Russia, and extra-European powers, especially the United States, would have profound consequences for Europe’s future in the 20th century, while internal mobilization for total war had already gone far to reshape European societies.