The First World War was an unprecedented catastrophe that shaped our modern world. For the last six years we’ve been covering the causes and major events of the war exactly 100 years after they happened. All the entries in the WWI Centennial blog are available in reverse chronological order, along with other stories about the war, here.
With the final climactic year underway, we’re also providing a (relatively) condensed version so new readers can catch up and long-time readers can refresh their memories.
1914: THE CONFLICT BEGINS
After the assassination of Archduke Franz Ferdinand by Bosnian Serb nationalists in Sarajevo, the leaders of the ailing Austro-Hungarian Empire decided to use the murder of the heir to the throne as a pretext to crush their troublesome neighbor, the Kingdom of Serbia, once and for all. With support from their powerful ally Germany, they delivered an ultimatum to Serbia with demands so outrageous it was guaranteed to be rejected, giving them an excuse to declare war.
But Germany and Austria-Hungary’s clumsy efforts to “localize” the conflict went off the rails in the “July Crisis.” After Austria-Hungary declared war on Serbia on July 28, on July 30 Serbia’s Slavic patron Russia mobilized against Austria-Hungary and Germany. On August 1 Germany declared war on Russia and its ally France, and on August 4 Britain declared war on Germany after German troops violated Belgian neutrality as part of the Schlieffen Plan.
As war rippled across the planet, fighting defied expectations on both sides. France’s attempt to reclaim Alsace-Lorraine ended in bloody defeat during the Battle of the Frontiers, while the Germans overcame the odds to destroy the Russian Second Army at Tannenberg, and Austria-Hungary suffered a humiliating defeat at the hands of the Serbs at Kolubara. In September Germany’s invasion of northern France failed decisively at the “Miracle on the Marne,” and the exhausted Germans retreated north and dug in, marking the emergence of trench warfare.
The opposing armies now tried to outflank each other again and again, without success, in the “Race to the Sea,” leaving parallel lines of trenches behind them, eventually reaching the North Sea in Flanders in western Belgium. Here the Germans made one last push to break through the Allied lines at Ypres (fated to be the scene of two more titanic battles in the years to come). As 1914 drew to a close, the horrific casualties shocked the world, and the entry of the Ottoman Empire into the war on the side of the Central Powers in November just spread the bloody stalemate further. However there was a brief moment of good cheer with the famous Christmas Eve Truce.
1915: GALLIPOLI AND THE GREAT RETREAT
The following year was marked by more disappointments and surprises. Frustrated on the Western Front, Britain and France tried, and failed, to knock the Ottoman Empire out of the war with a long shot attempt to “force” the Turkish straits with warships, followed by amphibious landings, resulting in an even worse defeat at Gallipoli.
Although the Turks held off the Allied attacks, the threat to the Turkish homeland, along with the fact that some Armenian Christians were helping their Russian co-religionists invade the empire, prompted the Ottoman “Young Turk” triumvirate to unleash the Armenian Genocide, killing around 1.5 million by 1917. At the same time, after a year of heated debate Italy—thinking Gallipoli was going to be a big Allied victory—finally joined the Allies with a declaration of war against Austria-Hungary, but immediately became bogged down in trench warfare as well.
In spring 1915 Germany outraged public opinion with two brutal new weapons: poison gas and submarine warfare. The German Fourth Army unleashed chlorine gas on Allied forces at the Second Battle of Ypres in April 1915, causing horrific casualties but ultimately failing to achieve a breakthrough, thanks to the bravery of Canadian troops; This set the pattern for the rest of the war, as both sides used poison gas to amplify the effects of artillery bombardments on enemy trenches—with terrible but rarely decisive effects.
Meanwhile Germany’s decision to mount unrestricted U-boat warfare brought her to the brink of war with the United States, the world’s most powerful neutral nation. The sinking of the Lusitania on May 7, 1915 infuriated the American public and pushed the U.S. towards the Allies (although there was also anger at the Allied blockade of the Central Powers, which hurt U.S. business interests). The Germans backed down, but remained determined to cut the Allies off from American industry, the key to sustaining the Allied war effort.
The summer of 1915 brought the first major breakthrough of the war on the Eastern Front, with the Central Powers’ rapid conquest of Russian Poland during the Gorlice-Tarnow campaign. The Russian Great Retreat, as it came to be known, was a huge setback, prompting Tsar Nicholas II to take over personal command of the Russian Army—meaning he would be held responsible for future defeats. And worse was to come for the Allies: in October 1915 Bulgaria joined the Central Powers and helped crush Serbia. The remnants of the Serbian Army managed to escape through Albania, and were subsequently evacuated by Allied ships to the island of Corfu. Eventually the Serbian Army was redeployed in Salonika in northern Greece, reinforcing Allied troops recently evacuated from Gallipoli in a belated effort to help Serbia from the south.
1916: CATASTROPHIC CASUALTIES
Some of the biggest battles in human history occurred in Europe the following year, beginning with the incredible German onslaught at Verdun in February 1916. A cold-blooded German plan to “bleed France dry” through simple attrition, Verdun soon spun out of control, resulting in almost as many casualties for the Germans as the French. The failure led to the firing of chief of the general staff Erich von Falkenhayn, replaced in September 1916 by Paul von Hindenburg (aided by his chief strategist, Erich Ludendorff).
In June 1916 the Russians launched their most successful offensive of the war by far, orchestrated by General Alexei Brusilov, a pioneer of “combined arms,” in which attacks by artillery, infantry and airplanes were carefully coordinated to punch holes in widely separated portions of the enemy front at once. The Brusilov Offensive, as it became known, resulted in the almost total collapse of the Austro-Hungarian armies in Galicia by September 1916, forcing Germany to withdraw troops from other parts of the front to prop up its beleaguered ally, at which point the Russian offensive sputtered.
The summer of 1916 was a grim time for the Central Powers, as the British also launched their biggest offensive of the war to date at the Somme. The Allies inflicted heavy casualties on the Germans but also suffered breathtaking losses, with 57,470 British casualties including 19,240 dead on the first day alone (July 1, 1916). In the weeks to come the British scored more victories, pushing the enemy back again and again, but the Germans were always able to dig into new defensive positions; the battlefield debut of tanks in September 1916 spread terror in the German ranks but failed to provide a decisive advantage.
In another case of bad timing, in August 1916 Romania—encouraged by Russian success in the Brusilov Offensive and the British advance at the Somme—joined the Allies in hopes of conquering Austria-Hungary’s ethnic Romanian provinces. However this soon proved a disastrous mistake, as Germany rushed more reinforcements to the Balkans and swiftly crushed the Romanians with help from the Austro-Hungarians, Bulgarians and Turks, occupying Bucharest by winter.
1917: THE U.S. ENTERS THE WAR
The fourth year of the war started and ended with upheaval. Leading the way was the Russian Revolution in March 1917, when workers and soldiers overthrew the Romanov Dynasty and seized power on behalf of the Duma, or parliament. However the new Provisional Government was always weak, forced to share power with the Petrograd Soviet, a socialist assembly representing soldiers and workers, and leftist radicals in the Soviet, including Lenin’s Bolsheviks, wanted to overthrow the Provisional Government too.
The radicals got a boost with the failure of the disastrous offensive ordered by War Minister Alexander Kerensky in July, followed by an abortive military coup led by a conservative general, Kornilov, which undermined popular support for the new regime. After their own failed coup attempt in July, the Bolsheviks finally succeeded in overthrowing the Provisional Government in November, supposedly seizing power on behalf of the socialist Soviets—but in reality for themselves. The Bolsheviks would soon take Russia out of the war, a huge setback for the Allies.
This wasn’t their only problem. In March 1917 the Germans made a surprise withdrawal to formidable new defenses on the Western Front, known as the Hindenburg Line, in order to shorten their line and free up forces to fight elsewhere. Following the bloody defeat of the French spring offensive on the Western Front, half the French Army mutinied in May 1917, paralyzing the French war effort. Although General Philippe Petain, the hero of Verdun, set about improving conditions and restoring order, it would take months before the French Army was able to mount a major offensive. To take the pressure off their weakened ally, the British launched a gigantic offensive at the Third Battle of Ypres, better known as Passchendaele, which achieved some gains, but again ultimately failed to break through the German lines. The stunning Italian defeat at Caporetto then forced the British to halt the offensive to reinforce the Italian front.
Fortunately for Britain and France, an even bigger ally was rumbling into action. Germany’s resumption of unrestricted U-boat warfare in February 1917, followed by the revelation of the Zimmermann Telegram, in which the Germans secretly encouraged Mexico to declare war on the U.S., outraged American public opinion so much that President Woodrow Wilson got Congress to declare war on Germany on April 4, 1917. But it would take time for the U.S. to build an army big enough to make a difference in Europe.
After the Bolsheviks agreed to an armistice in December, Russia’s exit from the war and descent into civil war spelled bad news for the Allies. As 1917 drew to a close, the big question was whether the Germans would be able to transfer troops from the Eastern Front and crush the overstretched British and French before American troops started arriving in large numbers? This was the final race that would decide the outcome of the war.