Nine kings gather for King Edward VII's funeral, marking the end of Europe's era of tense peace.

Germany finalizes the Schlieffen Plan, a strategy calling for a massive right-wing sweep through Belgium to rapidly defeat France.

The assassination of Archduke Franz Ferdinand triggers a chain of ultimatums across Europe, pulling the major powers toward war.

Germany issues an ultimatum demanding Russia halt its mobilization in support of Serbia.

Kaiser Wilhelm attempts to redirect all troops east and avoid war with France, but Chief of Staff Moltke refuses to alter the mobilization schedule.

After Belgium rejects Germany's demand for free passage, German troops cross the Belgian border.

Belgium's army resists the German advance at Liège, throwing Germany's carefully planned timetable into disarray.

The British Expeditionary Force debarks from England and marches into Belgium to support the French.

Germany brings up heavy artillery and destroys the Belgian forts surrounding Liège one by one.

The four-battle clash known as the Battle of the Frontiers ends in a devastating Allied retreat across the Western Front.

Germany encircles and obliterates the Russian 2nd Army at the Battle of Tannenberg, collapsing the Eastern Front threat.

German forces burn the Belgian city of Louvain, turning world opinion firmly and irrevocably against Germany.

The Allied armies fall into full retreat as the German army advances deep into France toward Paris.

General Von Kluck turns his army away from Paris to pursue and envelop the retreating French forces.

Joffre personally appeals to the British commander to join the French counterattack, launching the Battle of the Marne.

The Guns of August opens with King Edward VII's funeral, which signals the end of Europe's fragile peace, and traces Germany's activation of the Schlieffen Plan through Belgium after the assassination of Archduke Franz Ferdinand. Belgium's unexpected resistance at Liège disrupts Germany's timetable while the British Expeditionary Force rushes to join the fight, but the Allied armies are overwhelmed at the Battle of the Frontiers and pushed into full retreat. On the Eastern Front, Germany annihilates the Russian 2nd Army at Tannenberg, while in Belgium the burning of Louvain hardens the world's resolve against Germany. As the German army advances toward Paris, General Von Kluck's fateful decision to turn away from the city and pursue the retreating French exposes his flank. Joffre seizes the opportunity, personally rallying the British to fight alongside the French in the counterattack that becomes the Battle of the Marne, halting the German advance and dooming both sides to years of grinding attrition.

The war's defining moments from diplomatic collapse to the Battle of the Marne.

German General von Bernhardi publishes a book arguing that Germany must initiate war as a matter of national necessity.

France formally adopts Plan 17, committing entirely to an offensive strategy with no meaningful provisions for defense.

British General Wilson meets French General Foch, forming a military friendship that leads to the Dubail-Wilson agreement binding both armies together.

Russia's minister of war Sukhomlinov proudly declares he hasn't read a military strategy book in years, embodying the corruption crippling Russian command.

Churchill and Grey mobilize the British fleet in defiance of majority Cabinet opposition, betting Germany will justify their decision by morning.

Germany delivers a sealed ultimatum to Belgium falsely claiming France has attacked first and demanding free passage for German troops.

German Admiral Souchon raises a Russian flag and opens fire on Algerian coastal towns as war declarations are still being exchanged.

The British fleet pursues the German warship Goeben across the Mediterranean for days but fails to intercept it at every opportunity.

German forces shoot Belgian civilians and burn villages in retaliation for the fierce armed resistance they did not expect to face.

General Lanrezac repeatedly warns French high command about the massive sweeping German right wing, but his urgent reports are dismissed.

Germany transfers two army divisions from the Western Front to the Eastern Front to counter the advancing Russian forces.

France, Britain, and Russia sign the Pact of London, pledging that none will seek a separate peace with Germany.

Kitchener sails to Paris and confronts Sir John French, demanding the British Expeditionary Force remain committed alongside the French army.

Germany pre-manufactures victory medals celebrating its anticipated triumphant entry into Paris before the decisive battle has even been fought.

Gallieni commandeers Paris's civilian taxis to rush thousands of reserve troops to the front for the Battle of the Marne.

Before the war begins, Germany's intellectual culture produces open calls for war as national necessity, France locks itself into an offensive-only Plan 17, and England quietly binds its military to France through the Dubail-Wilson agreement despite strong antiwar sentiment at home. Russia's military, corrupted and backward-looking as embodied by War Minister Sukhomlinov, proves a far weaker ally than France and England hope for. As fighting breaks out, Germany's ultimatum to Belgium, Churchill and Grey's unauthorized fleet mobilization, and the German warship Goeben's escape to Turkey each ripple outward with enormous strategic consequences. On the ground, German atrocities against Belgian civilians, General Lanrezac's ignored warnings about the German right wing, and the transfer of two divisions to the Eastern Front all shift the balance of the war in subtle but decisive ways. The Pact of London commits the Allies against a separate peace, Kitchener forces Britain to stay in the fight, Germany's premature victory medals capture its fatal overconfidence, and finally Gallieni's commandeered taxis carry the reserves needed for the counterattack that saves Paris.

The strategic decisions, diplomatic failures, and battlefield turns that shaped the war.

Kaiser Wilhelm becomes convinced that King Edward VII deliberately built alliances with France and Russia to encircle and isolate Germany.

French General Michel is removed from command after proposing to attach reserve troops to frontline units to build a stronger defense.

British Foreign Secretary Grey drafts a deliberately vague commitment letter to France, carefully satisfying both pro-war and antiwar Cabinet factions.

King Albert of Belgium receives a telegram from Kaiser Wilhelm claiming Germany's invasion of Belgium is carried out with only the friendliest intentions.

Grey addresses the British Parliament, invoking English honor and warning that Germany could soon dominate all of continental Europe.

The German warship Goeben reaches the Dardanelles Strait and Turkey allows the ships to enter, quietly sealing a Germany-Turkey alliance.

Admiral Souchon commands the Goeben to shell the Russian Black Sea ports of Odessa and Sevastopol, drawing Turkey fully into the war.

The Belgian government and army retreat to Antwerp, successfully evading German encirclement and preserving Belgian forces for continued resistance.

German Prince Rupprecht launches a full counterattack against French forces in Lorraine, abandoning Germany's original defensive plan for that flank.

Germany intercepts uncoded Russian wireless transmissions revealing exact troop positions and movements ahead of the decisive Battle of Tannenberg.

General Samsonov cuts communications with the Russian rear command and rides personally into battle as his army collapses around him.

A British newspaper publishes a frank account of the losses at Mons, shattering public confidence that the war was going well.

French reconnaissance aircraft spot Von Kluck's army turning away from Paris, revealing an exposed German flank ripe for a counterattack.

Sir John French countermands his own assurances and orders the British Expeditionary Force not to join the French counterattack on the Marne.

Moltke dispatches orders to halt the German advance, but the orders arrive too late and Von Kluck continues his fatal march.

The war's roots lie partly in Kaiser Wilhelm's deep conviction that Edward VII conspired to encircle Germany, while France's capacity for defense is gutted when General Michel is dismissed for proposing a more cautious strategy, and Grey's deliberately vague diplomatic letter reveals how England edges into the conflict driven as much by honor and fear as by treaty. King Albert's receipt of the kaiser's absurd friendly-invasion telegram and Grey's rousing Parliament speech mark the moment Europe fully commits to war, while at sea the Goeben's passage through the Dardanelles seals the Germany-Turkey alliance, and the subsequent shelling of Russian Black Sea ports drags Turkey's entire neighborhood into the conflict. On the Eastern Front, Germany's interception of unencrypted Russian wireless messages proves decisive at Tannenberg, where General Samsonov's personal ride into the collapsing battle underscores the human cost of institutional failure. Back in the West, a newspaper's honest account of British losses shatters home-front illusions, while a reconnaissance aircraft's identification of Von Kluck's exposed flank provides the crucial intelligence for a counterattack. The final fumbling of both Sir John French and Moltke—one countermanding his own promises, the other sending orders that arrive too late—seals the outcome of the Battle of the Marne and the fate of the war.

The revelations, pivotal choices, and turning points that determined the war's course.