NOTE: Not mine, off of another alternate history site, I do not claim this.
Point of Divergence is in September 1918: the Entente offensive in the Balkans failed. Why this POD in a secondary front? Because, until September 1918, Germany and Austria-Hungary were exhausted, but they resisted to Entente pressure: Germans retreat in France and Belgium was well orchestrated and they could have hold the new defensive Muse-Antwerp line. Austria-Hungarian armies could have contained a new Italian offensive. Ottoman Empire could have resisted in Anatolia (where the Young Turks prepared a defense in depth) after the losses of Syria and Mesopotamia. In 1918 Enver Pasha was planning a new offensive in Central Asia. Internal disorders in Germany and Austro-Hungary were under control until October 1918 and they broke out seriously only after the beginning of peace negotiations. Well, only in the end of September, after the fall of Bulgaria, Ludendorff lost all his hopes (and his mental stability) and asked for peace. From October to November Central Powers fell like a cardboard castle. Let’s imagine this new timeline starting from September 1918:
September – December 1918: the new stalemate
Bulgaria and German forces on Southern Front stopped the Entente advance. Austria-Hungarian western forces preceded the Italian move against Piave river and evacuated Veneto. They succeeded in re-establishing the old Isonzo line. On 30 October, Germany launched her greatest naval attack against the Thames and the Flanders coast. This attack resulted in a severe defeat for the German High Sea Fleet: intercepted by the Grand Fleet near Terschelling Island, German fleet didn’t repeat the “miracle” of Jutland and lost most of its best modern ships (almost all the battlecruisers, the Bayern class dreadnoughts and many other capital ships). But the German action close to London resulted in an unprecedented shock for British people. The naval attack persuaded London, Paris and Washington to continue the war until the unconditional surrender of Central Powers. British naval aviation attacks Wilhelmshaven naval base on November, inflicting other serious damages to German’s capital ships. American and British bombers conducted the first air raid over Berlin on December. This bombardment induces German civilians to continue the war to the death. Political divergences of this period: the mid-term elections in Us gave the victory to Democrats, the president’s party. In Germany, the Kaiser gave generals Hindenburg and Ludendorff and admiral Scheer almost dictatorial power.
January – February 1919: the opposite plans
Central Power’s plan for the Fifth year of war is simple: resist in the Western and Southern fronts, launch a new lightening offensive in the East, continue with the unrestricted submarine warfare. Central Power’s high commands hope that mutinies, pro-communist rebellions and Spanish flu can undermine the Entente Power’s morale and induce them to a negotiated peace. The theater for the only offensive in the East is Central Asia: few Germans and Ottomans divisions, starting from the occupied Caucasus, have to occupy the Eastern coast of Caspian Sea, liberate German and Austrian prisoners and march into Russian Turkestan. The main goal is Afghan and Indian frontiers: joining it could provoke a rebellion of local peoples against the British. Entente’s plan for the Fifth year of war means simply: an invasion of Germany from France and Belgium. The plans (based on Plan 1919 by JFC Fuller) prescribed: a large number of tanks, speed and an innovative use of the aviation as a tactical support for the troops. The Entente would launch secondary offensives against the other fronts: Italians led the offensive against AH line aiming at Trieste; a new Entente offensive against Bulgaria; an offensive against the heart of Ottoman defenses in Anatolia; secondary operations in Northern and Eastern Russia to help White Armies against the Red Army and the Central Power’s occupation forces. Political divergences: a non-aggression pact was signed with the Bolshevik regime in Moscow. In the Middle East, on 3 January, Zionist leader Chaim Weizmann and Arabian prince Feisal Al Hashemite signed a mutual recognition agreement (like in the OTL) and they added a military protocol to it: the Jewish and Arabian Legions became co-belligerent units under the British command, to continue the war against the Ottoman Empire. They will form the nucleus of the two future national armies of a Jewish Palestine and an independent Arabian Kingdom in Syria. On January the elections in Great Britain resulted in a complete victory for Lloyd George. The Prime Minister choose Winston Churchill for the Ministry of War (as in the OTL). Churchill was determined to end the Bolshevik regime in Russia and create a Jewish Palestine in the Middle East. In February, Germany and Austria-Hungary signed a new added protocol to Brest-Litovsk treaty: non-aggression and cooperation between Central Powers and the Bolshevik regime in all Russian theater of operations. Entente (despite the harsh opposition of Woodrow Wilson) finally recognizes the Omsk government (led by adm. Kolchak) as the only legitimate Russian government. Both sides take little action during winter, because of exhaustion, the lethal effects of Spanish flu (which decimated entire divisions on both sides) and cold weather. But the next spring the final clash begins.
March – April 1919: the opening moves
the first move of the 1919 was the German-Ottoman offensive against Persia and former Russian Turkestan. A first Ottoman column occupied Enzeli, Resht and Kazvin (northern Persia) securing the southern cost of Caspian Sea. They defeated Persian kossaks supported by British light units (the “Dunsterforce”). The main German-Ottoman expeditionary force, supported by Bolshevik’s naval light units, occupied the harbour of Krasnovodsk, eastern coast of Caspian Sea. They advanced until Ashkabad encountering virtually no resistence. They liberated some 40.000 German and Austrians prisoners who join the advance.
pressed by the events in the Central Asian front, British general Marshall (in Mosul) and Allenby (in Aleppo) decided a coordinated offensive aimed at Nisibin, southern Anatolia. General Marshall’s troops pushed the Ottoman VI Army to north; Allenby (whose forces comprise Jewish and Arabian Legions) advanced to Nisibin encountering virtually no resistence
Admiral Kolchak launched his great offensive on 2 March; from Siberia, Kolchak’s Army broke Bolshevik’s lines and advanced toward West with the support of American and Japanese divisions; in the end of April, his troops and Entente’s forces reached the line of Ural and Kama rivers; from Murmansk and Arkangelsk, American and British expeditionary corps attacked Red Army's positions aiming to join Kolchak’s advance; in the end of April, Ural kossaks and Bashkir troops (under the command of Alexandr Dutov) moved south to stop the German-Ottoman advance in Turkestan
Heavy casualtis (provoked by Spanish flu) and bad weather oblige Entente and Germans to little activities along this front; Haig and Pershing (British and American commanders) wait for the new generations of tanks (Mark VIII “Liberty” and Medium C) before any new advance against the enemy’s fortified lines.
Italian army received and deployed its first tank unit (with French Ft-17) in January. On first days of April, general Armando Diaz launched his attack against Isonzo line, using the tanks against the Carso sector. The main effort was conducted by the Italian III Army which broke enemy lines during the first days: Austro-Hungarian VI Army (decimated during 1918 campaign and by Spanish flu… Austro-Hungarian losses were the highest during the pandemia) panicked and fell. In the end of April, Italians occupied Trieste, their main target since the beginning of the war.
nothing relevant in this period
War on the sea
German submarines continued their attacks against Atlantic convoys; British anti-submarine units began to use extensively the first model of Sonar, with very lethal effects on the enemy; British aircraft carrier HMS Furious and land-based naval aviation launched a new attack against Wilhelmshaven, inflicting severe losses to the German High Seas Fleet.
the Bolshevik-German pact began to produce its effects and anti-war/pro-communist uprisings broke out in France, Great Britain and Italy; German-Ottoman advance in Central Asia began to provoke minor uprisings in Afghanistan and India against British rule; minor nationalist uprisings were registered inside Autro-Hungarian army; in Germany the situation was under control.
May – June 1919: Central Powers hope for revolution
The German-Ottoman advance reach the Persian city of Mashhad and provoked a huge rebellion into Afghanistan against British rule; the appeals for a Jihad, launched by Mehemet VI reached also Indian Muslim masses, who started a large rebellion against the British forces in Pakistan; the newly independent khanates of Bukhara and Kiva declared war to Great Britain; the old Kitchener’s nightmare (a global Jihad against the Empire, as in the romance “Greenmantle”) almost became a reality; but British forces (with massive use of air raids) repressed the Afghan and Indian rebellions; in Mashhad, German-Ottoman forces were stopped and severely defeated in a large field battle by the British-Indian expeditionary force led by gen. Wilfred Malleson; the attack on Ashkabad led by Dutov’s Siberian and Bashkir Cossacks broke the supply lines of the German-Ottoman columns, inflicting them a definitive defeat.
Allenby and Marshall joined forces around Nisibin; Ottoman’s VI Army and other Turkish forces were catch between two fronts and surrendered after a desperate resistance; in the Mediterranean sector, British forces occupied Alexandretta.
Kolchak’s White Army, supported by American, Japanese and Czech divisions, continued its advance in Siberia, seizing the cities of Kazan, Nizhny Novgorod, Samara and Saratov; in Tzaritzin (on Volga river), Kolchak’s Army joined its forces with Denikin’s White Army; along the Sukhona river, Kolchak’s army join forces with the Anglo-American arctic forces and Evegune Miller’s White Army; in the end of June, White Armies were deployed along an uninterrupted front from Arctic to Black Sea. They occupied a large territory with 5 millions inhabitants, their forces doubled. And they were ready to advance to Moscow as a steamroller. Germany signed a new pact with Bolshevik regime to avoid its sudden collapse and the re-opening of an Eastern front. Two German Army Corps were transferred from Western to Eastern front. Central Powers occupation forces in Belarus, Baltics States and Ukraine were alerted and readied to fight side by side with the Red Army.
Entente’s forces began their preliminary offensives in the end of June; Belgians supported by British II Army (with tanks) broke German’s lines and liberated Antwerp; new tanks and the lessons of general J.F.C. Fuller (an armored fist supported by tactical air raids) were applied for the first time with success; using similar tactics, American and French forces broke the German lines in Metz and occupied the city in few days.
Italian III and VIII Armies (with 6 British and French divisions) push Austro-Hungarian VI Army troops inside the Istria Peninsula and completed a successful advance reaching Fiume in the end of June
General Franchet d’Esperey launch a new offensive in Macedonia in the end of June; the Entente’s “Eastern Army” broke the enemy lines (held by German and Bulgarian forces) on 30 June.
War on the sea
The almost complete destruction of the German fleet induced admiral David Beatty to penetrate the Baltic Sea (completely controlled by Germans since 1914); the Grand Fleet entered the Baltic in the end of June through the Grand Belt, losing few ships because of minefields; in the Atlantic ocean, British anti-submarine units, thanks to the sonar, wiped out German submarine forces; the German’s indiscriminate submarine campaign was virtually terminated in the end of June.
the German-Bolshevik pact produced strange effects. In Germany the Spartacist movement began to support Hindenburg-Ludendorff's command. The OHL gave the Army and Navy units the possibility to form new Soviets, loyal to German's cause. The German military and political system remained the same. The rhetoric and the ideology changed: the 1918 opposition was no more opposed to government. Where Entente's forces fought for national self-determination and democracy (since the proclamation of Wilson's 14 points), the Germans, after the German-Bolshevik pact, began to fight for Socialism (which was an integral part of German nationalism since the beginning of the war). In Moscow, Lenin and Trotsky didn't appreciate this kind of National-Socialism. But they accepted it as a first step for the next European revolution. And because they need German's support. Inside Entente's continental powers, Bolshevik's propaganda was really strong in France, Britain and Italy. Little civil wars broke out inside those countries, barely contained by regular armies.