First Army (United Kingdom) in the context of "18th Army Group"

The Western Desert campaign (Desert War) took place in the deserts of Egypt and Libya and was the main theatre in the North African campaign of the Second World War. Military operations began in June 1940 with the Italian declaration of war and the Italian invasion of Egypt from Libya in September. Operation Compass, a five-day raid by the British in December 1940, was so successful that it led to the destruction of the Italian 10th Army (10ª Armata) over the following two months. Benito Mussolini sought help from Adolf Hitler, who sent a small German force to Tripoli under Directive 22 (11 January). The Afrika Korps (Generalleutnant Erwin Rommel) was formally under Italian command, as Italy was the main Axis power in the Mediterranean and North Africa.

In the spring of 1941, Rommel led Operation Sonnenblume, which pushed the Allies back to Egypt except for the siege of Tobruk at the port. At the end of 1941, Axis forces were defeated in Operation Crusader and retired again to El Agheila. In early 1942 Axis forces drove the Allies back again, then captured Tobruk after the Battle of Gazala but failed to destroy their opponents. The Axis invaded Egypt and the Allies retreated to El Alamein, where the Eighth Army fought two defensive battles, then defeated the Axis forces in the Second Battle of El Alamein in October 1942. The Eighth Army drove Axis forces out of Libya to Tunisia, which was invaded from the west by the Allied First Army in Operation Torch. In the Tunisian campaign the remaining Axis forces surrendered to the combined Allied forces in May 1943.

The Nivelle offensive (16 April – 9 May 1917) was a Franco-British operation on the Western Front in the First World War which was named after General Robert Nivelle, the commander-in-chief of the French metropolitan armies, who led the offensive. The French part of the offensive was intended to be strategically decisive by breaking through the German defences on the Aisne front within 48 hours, with casualties expected to be around 10,000 men. A preliminary attack was to be made by the French Third Army at St Quentin and the British First, Third and Fifth armies at Arras, to capture high ground and divert German reserves from the French fronts on the Aisne and in Champagne. The main offensive was to be delivered by the French on the Chemin des Dames ridge (the Second Battle of the Aisne). A subsidiary attack was to be made by the Fourth Army (the Third Battle of Champagne). The final stage of the offensive was to follow the meeting of the British and French armies, having broken through the German lines, to pursue the defeated German armies towards the German frontier.

The Franco-British attacks were tactically successful; the French Third Army of Groupe d'armées du Nord (GAN, Northern Army Group) captured the German defences west of the Hindenburg Line (Siegfriedstellung) near St Quentin from 1 to 4 April, before further attacks were repulsed. The British Third and First armies achieved the deepest advance since trench warfare began, along the Scarpe river in the Battle of Arras, which inflicted many casualties on the Germans, attracted reserves and (specifically the four Canadian divisions of the First Army) captured Vimy Ridge to the north. The main French offensive on the Aisne began on 16 April and also achieved considerable tactical success but the attempt to force a strategically decisive battle on the Germans was a costly failure and by 25 April the main offensive had been suspended.

The Battle of Arras, also known as the Second Battle of Arras, was a British offensive on the Western Front during the First World War. From 9 April to 16 May 1917, British troops attacked German defences near the French city of Arras on the Western Front. The British achieved the longest advance since trench warfare had begun, surpassing the record set by the French Sixth Army on 1 July 1916 in the First day on the Somme. The British advance slowed in the next few days and the German defence recovered. The battle became a costly stalemate for both sides and by the end of the battle, the British Third Army and the First Army had suffered about 160,000 casualties and the German 6th Army about 125,000.

For much of the war, the opposing armies on the Western Front were at a stalemate, with a continuous line of trenches from the Belgian coast to the Swiss border. The Allied objective from early 1915 was to break through the German defences into the open ground beyond and engage the numerically inferior German Army (Westheer) in a war of movement. The British attack at Arras was part of the Anglo-French Nivelle Offensive, the main part of which was the Second Battle of the Aisne 50 mi (80 km) to the south. The aim of the French offensive was to break through the German defences in forty-eight hours. At Arras the Canadians were to capture Vimy Ridge, dominating the Douai Plain to the east, advance towards Cambrai and divert German reserves from the French front.