Question: What was the first battle in World War I?

List of military engagements of World War I

List of military engagements of World War I encompasses land, naval, and air engagements as well as campaigns, operations, defensive lines and sieges. Campaigns generally refer to broader strategic operations conducted over a large bit of territory and over a long period of time. Battles generally refer to short periods of intense combat localised to a specific area and over a specific period of time. However, use of the terms in naming such events is not consistent. For example, the First Battle of the Atlantic was more or less an entire theatre of war, and the so-called battle lasted for the duration of the entire war.[1]

Western Front

The Western Front comprised the frictinous borders between France, Germany, and the neighboring countries. It was infamous for the nature of the fight that developed there; after almost a full year of inconclusive fighting, the front had become a giant trench line stretching from one end of Europe to the other.[1]
1914
Battle of Liège

The Battle of Liège was the first battle of the war, and could be considered a moral victory for the allies, as the heavily outnumbered Belgians held out against the German Army for 12 days. From 5–16 August 1914, the Belgians successfully resisted the numerically superior Germans, and inflicted surprisingly heavy losses on their aggressors. The German Second Army, comprising 320,000 men, crossed into neutral Belgium in keeping to the Schlieffen Plan, with the ultimate goal of attacking France from the north. Liège was key strategically as it held a position at the head of a pass through the Ardennes, which made it the best possible route into the heart of Belgium itself.[2]
The city was surrounded by a ring of 12 heavily armed forts, garrisoned by 70,000 men under the command of Gérard Leman. A night attack on 5 August was repulsed with heavy losses to the Germans, to the extreme surprise of the supremely confident German army. The next day, rather than confront the forts in battle, the German commander Erich Ludendorff attacked the city through the back, through a break in the line of fortresses that the Belgians had intended to fortify, but never did so. Although they succeeded in capturing the city, the Germans knew that they could not continue advancing troops into Belgium without first breaking down the forts. Aided by 17-inch Howitzers, the Germans finally succeeded in bringing down the forts on 16 August.[2]
The unprecedented Belgian resistance seriously prolonged the opening German assault at the outbreak of World War I, allowing France and Britain time to organize themselves and a defense of Paris. In addition, it was an important moral victory for the Allies.
Battle of the Frontiers
The early French initiative, to recapture territory lost to the Germans in the 1870–1871 Franco-Prussian War, was played out in a series of frontier battles between the Germans and the French, known collectively as the Battle of the Frontiers. The battles at Mulhouse, Lorraine, the Ardennes, Charleroi, and Mons were launched more or less simultaneously, and marked the collision of the German and French war plans, the Schlieffen Plan and Plan XVII, respectively.[1][3]
Battle of Mulhouse
The Battle of Mulhouse was the opening attack by the French against the Germans. The battle was part of a French attempt to recover the province of Alsace, which had been lost as a consequence of having lost the Franco-Prussian War of 1870–1871. A French force under General Louis Bonneau detached from the French First Corps and invaded the frontier on August 8, 1914. Opposing them was the German 7th Division. The recapture of the area, preordained by the French Plan XVII, was to boost national pride—and to provide a guard force for the flank of subsequent invasions.[4]
The French quickly recaptured the border town of Altkirch with a bayonet charge. Bonneau, suspicious of the little German resistance, was wary of a carefully planned German trap. However, under orders the next day he advanced to Mulhouse, capturing it with little effort, for the Germans had already abandoned it.[4]
In France, the retaking of Mulhouse, without a fight, was celebrated greatly. However, with the arrival of German reserves from Strasbourg, the tides were turned, and the Germans mounted a counter-attack on nearby Cernay. Unable to mount an all-encompassing defense, and unable to call on reserves of his own, Bonneau began a slow withdrawal from the region. Support troops hastily sent by the French commander-in-chief Joseph Joffre arrived too late to prevent Bonneau from retiring. Joffre was immensely angry with Bonneau, charging him with a "lack of aggression" and immediately relieving him of command. Realizing the psychological magnitude of the loss, he assembled a force, led by Paul Pau, which tried unsuccessfully to recapture the province.[4]
Battle of Lorraine

The invasion and recapture of Lorraine formed one of the major parts of the French pre-war strategy, Plan XVII. The loss of Lorraine (and Alsace; see above) to the Prussians in the 1870-1871 Franco-Prussian War was seen as a national humiliation by the public and military alike, and was at the forefront of their minds for the next war against the Germans.[5]
The battle was initiated by the French First and Second armies. The First, led by General Auguste Dubail, intended to take Sarrebourg, whilst the Second, led by General Noel de Castelnau, intended to take Morhange. Both towns were well fortified, and the task of defending them fell to Crown Prince Rupprecht, who had overall control of the German Sixth and Seventh armies.[5]
Rupprecht adopted a strategy in which he would fall back under the French attacks, then counter-attack once he lured the French all the way to his fortifications. As the French army advanced, it met stern resistance in the form of German artillery and machine-gun fire. Army Chief of Staff Helmuth von Moltke authorized a more aggressive tactic soon after, and on August 20, the German army started to roll back the French. Caught by surprise and without the assistance of entrenched positions, the Second Army was pushed back quickly, eventually into France itself. A gap was exposed between the forces in Mulhouse and those in Lorraine; the forces in Mulhouse were withdrawn to keep the gap from being taken advantage of by the Germans.[5]
Diverging from the Schlieffen Plan, Rupprecht received reinforcements and attacked the French line near the Trouée de Charmes; however, through the use of reconnaissance aircraft, the French spotted the German buildup, and were able to build an adequate defence. Thus the German gains were minimized, and were eradicated by a following French counter-assault on the 25th. Fighting continued there until the end of August, and quickly ground into a stalemate and trench warfare.[5]
Battle of the Ardennes
The Battle of Ardennes, fought between 21 and 23 August 1914, was another of the early frontier battles, conducted during the first month of the war. The battle was sparked by the mutual collision of French and German invasion forces in the lower Ardennes Forest.[6]
The pre-war French strategy expected German forces in the area to be light, and the French light, rapid firing artillery was expected to convey an advantage in forested terrain over the bigger German guns. Instead, it became increasingly apparent to all of the commanders in the region that a significant enemy presence was gathering, for the Germans had planned an offensive through the area.[6]
The sets of armies joined battle on both sides. General Pierre Ruffey's Third Army to the south and Fernand de Langle de Cary's Fourth Army to the north, fighting Germany's Fourth, led by Duke Albrecht, and Fifth army, led by Crown Prince Wilhelm.[6]
The German troops started moving through the forest on 19 August. Conditions worsened, and by the time the two armies met, the forest was covered in a deep fog, resulting in the two forces stumbling into one another. At first, the French took the Germans as a light screening force; however, in reality the French were heavily outnumbered. The first day of the battle consisted of light skirmishes; the main battle did not begin until 21 August.[6]
According to the pre-war French strategy document, Plan XVII, German forces in the area were only expected to be light, with French light, rapid-firing artillery proving advantageous in a wooded terrain such as that found in the Ardennes. However, what emerged was totally opposite; the French eagerly charged at German positions in the woods, and were mowed down by machine-gun fire. The French armies retreated hurriedly in the face of superior German tactical positioning, and the Germans chased them all the way back into the French border. In addition to losing a key strategic position, the French forfeited iron resources in the region as well.[6]
Battle of Charleroi
The Battle of Charleroi, another of the frontier battles, was an action taking place 12–23 August 1914. The battle was joined by the French Fifth Army, advancing north towards the River Sambre, and the German Second and Third armies, moving southwest through Belgium. The Fifth army was meant to join the Third and Fourth armies in their attack through the Ardennes. However, this plan was put into effect assuming the Germans were not considering an assault further north, through Belgium—which was the German plan all along. Charles Lanrezac, commander of the Fifth Army, was strongly against the idea, fearing an attack from the north. However Joseph Joffre, chief-of-staff, rejected any such idea; after much persuassion, Lanrezac finally convinced him to move the Fifth Army northwards.
However, by the time the Fifth Army arrived, units of the German Second Army were already in the area. Joffre authorized an attack across the Sambre, predicting that the German force had 18 divisions, comparable to Lanrezac's 15, plus another 3 British reinforcements (the British Expeditionary Force). However, Lanrezac predicted much higher numbers, closer to the actual number—32 German divisions. He preferred to wait for reinforcements, however that same day the Germans attacked across the river and established two beachheads, neither of which fell despite several French counterattacks.
The next day, the main attack began; the fighting carried on through the day, and into the next. The French centre suffered severe losses and retreated; but the west and east flanks both held their ground. However, the retreat of cavalry divisions to the far west exposed the French west flank. With news of his situation, and the fact that his flanks could give and be completely enwrapped, Lanrezac ordered a general retreat into northern France.
Siege of Maubeuge
The French town of Maubeuge was a major fort on the French side of the border. With a junction of no fewer than five major railway lines, it was recognized as a key strategic position by both sides; hence the construction of 15 forts and gun batteries ringing it, a total of 435 guns, and a permanent garrison of 35,000 troops. These were further bolstered by the choosing of the town as the advance base of the British Expeditionary Force. However, when these and the French Fifth Army retreated following the events at Charleroi, the town was cut off from allied support, and subsequently besieged on August 25. The German heavy artillery succeeded in demolishing the key forts around the city, and General Joseph Anthelme Fournier, in command of the garrison in the city, surrendered to the Germans some 13 days later.[7]
1914
Battle of Le Cateau
Battle of St. Quentin, also called the Battle of Guise
First Battle of the Marne
First Battle of the Aisne
Siege of Antwerp
First Battle of Albert
First Battle of Arras
Battle of the Yser
First Battle of Ypres
First Battle of Champagne
1915
Battle of Neuve Chapelle
Second Battle of Ypres
Second Battle of Artois
Battle of Loos
Second Battle of Champagne
1916
Battle of Verdun
Battle of Hulluch
Battle of the Somme
Battle of Fromelles
Battle of Pozières
Battle of Ginchy
1917
Nivelle Offensive
Battle of Arras (1917)
Battle of Vimy Ridge
Second Battle of the Aisne, also called the Third Battle of Champagne
Battle of Messines
Third Battle of Ypres, also called the Battle of Passchendaele
Battle of La Malmaison
Battle of Cambrai (1917)
1918
German Spring Offensive
First Battle of the Somme (1918), also known as the Battle of St. Quentin or the Second Battle of the Somme (to distinguish it from the 1916 battle)
Battle of the Lys, also known as the Fourth Battle of Ypres and the Battle of Estaires
Third Battle of the Aisne
Battle of Cantigny
Battle of Belleau Wood
Second Battle of the Marne
Battle of Soissons (1918)
Battle of Château-Thierry (1918)
Hundred Days Offensive
Battle of Amiens
Second Battle of the Somme (1918), also known as the Third Battle of the Somme
Battle of Saint-Mihiel
Battle of Epéhy
Battle of the Hindenburg Line
Meuse-Argonne Offensive, also called the Battle of the Argonne Forest
Battle of Cambrai (1918)
Battle of the Sambre (1918), also known as the Second Battle of the Sambre
Italian Campaign
First Battle of the Isonzo
Second Battle of the Isonzo
Third Battle of the Isonzo
Fourth Battle of the Isonzo
Fifth Battle of the Isonzo
Trentino Offensive or the "Battle of Asiago"
Sixth Battle of the Isonzo or the "Battle of Gorizia"
Seventh Battle of the Isonzo
Eighth Battle of the Isonzo
Ninth Battle of the Isonzo
Tenth Battle of the Isonzo
Eleventh Battle of the Isonzo
Twelfth Battle of the Isonzo or the "Battle of Caporetto"
Battle of the Piave River
Battle of Vittorio Veneto
Eastern Front
1914
Battle of Stalluponen
Battle of Gumbinnen
Battle of Tannenberg
Battle of Galicia
First Battle of the Masurian Lakes
Battle of the Vistula River
Battle of Łódź (1914)
Battle of Limanowa
1915
Siege of Przemysl
Battle of Bolimov
Second Battle of the Masurian Lakes
Great Retreat (Russian)
Sventiany Offensive
1916
Lake Naroch Offensive
Brusilov Offensive
1917
Kerensky Offensive
Russian Revolution
1918
Operation Faustschlag
Romanian Campaign
1916
Battle of Transylvania (Central Powers Victory)
Battle of Turtucaia (Central Powers Victory)
Battle of Dobrich (Bulgarian Victory)
First Battle of Cobadin (Romanian-Russian Victory)
Battle of Sibiu (1916) (Central Powers Victory)
Battle of Olt Valley (Romanian Victory)
Battle of Turnu Roșu Pass (Romanian victory)
Flămânda Offensive (Central Powers Victory)
Battle of Brașov (1916) (Central Powers Victory)
Battle of Bran-Câmpulung Area (Romanian Victory)
Battle of Prahova Valley (Romanian Victory)
First Battle of Oituz Pass (Romanian Victory)
Second Battle of Cobadin (Central Powers Victory)
First Battle of the Jiu Valley (Romanian Victory)
Second Battle of the Jiu Valley (Central Powers Victory)
Battle of Vulcan Pass (Central Powers Victory)
Second Battle of Oituz Pass (Romanian Victory)
Battle of Târgu Jiu (Central Powers Victory)
Battle of Robănești (German Victory)
Battle of Bucharest (Central Powers Victory)
Prunaru Charge (Central Powers Victory)
Battle of the Argeș (Central Powers Victory)
Battle of Râmnicu Sărat (Central Powers Victory)
1917
Battle of Tulcea (Romanian Victory)
Battle of Mărăști (Romanian-Russian Victory)
Battle of Mărășești (Romanian-Russian Victory)
Battle of Oituz (1917) (Romanian-Russian Victory)
Caucasus Campaign
Battle of Sarikamish (December 1914 - January 1915)
Battle of Manzikert (1915)
Battle of Kara Killisse
Battle of Koprukoy
Battle of Erzurum
Battle of Erzincan
Battle of Baku
Serbian Campaign
Battle of Cer
Battle of Drina
Battle of Kolubara
Battle of Morava
Battle of Kosovo (1915)
Battle of Ovche Pole
Gallipoli Campaign

The Gallipoli Campaign (also called the "Dardanelles Campaign"), was a number of battles fought between 1915 and 1916.
Battle of the Nek
Battle of Chunuk Bair
Battle of Gully Ravine
Battle of Hill 60 (Gallipoli)
Battle of Krithia Vineyard
Battle of Lone Pine
Battle of Sari Bair
Battle of Scimitar Hill
Landing at Anzac Cove
Landing at Cape Helles
First Battle of Krithia
Second Battle of Krithia
Third Battle of Krithia
Naval operations in the Dardanelles Campaign
Macedonian Front
Battle of Krivolak
1st Battle of Doiran
Battle of Florina
Battle of Struma
Monastir Offensive
Battle of Malka Nidzhe
Battle of Kajmakchalan
1st Battle of Cerna Bend
2nd Battle of Doiran
2nd Battle of Cerna Bend
Battle of Skra-di-Legen
Vardar Offensive
Battle of Dobro Pole
3rd Battle of Doiran
Sinai and Palestine Campaign
First Suez Offensive
Battle of Romani or "The Second Suez Offensive"
Battle of Magdhaba
Battle of Rafa
Battle of Mughar Ridge
Battle of Jerusalem
Fall of Damascus
First Battle of Gaza
Second Battle of Gaza
Third Battle of Gaza or the "Battle of Beersheba"
Battle of Beersheba
Battle of Megiddo
Mesopotamian Campaign
Fao Landing
Fall of Basra
Battle of Qurna
Capture of Amara
Battle of Nasiriyeh
Battle of Es Sinn
Battle of Ctesiphon
Siege of Kut
Battle of Sheikh Sa'ad
Battle of the Wadi
Battle of Hanna
Battle of Dujaila Redoubt
First Battle of Kut
Battle of Khanaqin
Second Battle of Kut
Fall of Baghdad
Samarrah Offensive
Battle of Jebel Hamlin
Battle of Istabulat
Battle of Ramadi
Capture of Tikrit
Battle of Sharqat
African Campaign
Fall of Cameroon
Fall of German South-West Africa (Namibia)
Fall of Togo
Fall of German East Africa
Battle of Tanga or Battle of the Bees
Battle of Rufiji Delta
Battle of Kilimanjaro
Battle of Sandfontein
Battle of Segale
Naval engagements

Atlantic Theatre
First Battle of Heligoland Bight (1914)
Battle of Coronel (1914)
Battle of the Falkland Islands (1914)
Raid on Scarborough, Hartlepool and Whitby (1914)
Battle of Dogger Bank (1915)
Otranto Barrage (1915–1918)
Battle of Jutland (1916)
Battle of Dover Strait (1917)
Second Battle of Heligoland Bight (1917)
Zeebrugge Raid (1918)
Mediterranean
Pursuit of Goeben and Breslau (1914)
Naval operations in the Dardanelles Campaign (1915–1916)
Battle of the Otranto Straits (1917)
Asia-Pacific Theatre
Battle of Rabaul
Battle of Tsingtao (1914)
Battle of Penang (1914)
Battle of Coronel (1914)
Battle of Cocos (1914)
Air engagements
World War I was the first war to see major use of planes for offensive, defensive and reconnaissance operations, and both the Entente Powers and the Central Powers used planes extensively. Almost as soon as they were invented, planes were drafted for military service.
See also the following articles:
Aviation in World War I
Aviation history (1914-1918)
Flying aces
List of World War I flying aces
Strategic bombing during World War I
Zeppelins in World War I
Contemporary wars
Some historians consider these conflicts to be part of the First World War, having started either during or just after the war. 
In some cases, these conflicts were not directly caused by the war yet were exacerbated by them. For example, the 1916 Easter Rising was caused by factors generally unrelated to the war in Europe, yet took place at the time it did due to the British Army being thinly stretched in 1916, as well as the promise of German support in fighting the British, among many other factors.
Others, such as the Mexican Revolution, began before but influenced the war in terms of materiel or as factors taken into consideration by the belligerents. In the cause of the Ottoman Wars, these motivated the Young Turks to move towards war against the Allied Powers.
Pre-First World War
Mexican Revolution (1910–1920)
Italo-Turkish War (1911-1912)
First Balkan War (1912–13)
Second Balkan War (1913)
Zaian War (1914-21)
During the First World War
Maritz Rebellion (1914–15)
Easter Rising (1916)
Warlord Era (1916–1928)
Senussi Campaign (1915–17)
Russian Revolution (1917)
Finnish Civil War (1918)
Russian Civil War (1918–22)
North Russia Campaign (1918–19)
Russian westward offensive (1918–19)
Post-First World War
Greater Poland Uprising (1918–19)
Hungarian-Romanian War (1918–19)
Polish-Soviet War (1919–21)
Irish War of Independence (1919–21)
Turkish War of Independence (1919–23)
Greco-Turkish War (1919–22)
Vlora War (1920)
Irish Civil War (1922–23)


Sources