He was Chief of the Imperial General Staff (CIGS), the professional head of the British Army, during the Second World War, and was promoted to field marshal on 1 January 1944.

[11] During the war, he was assigned to an ammunition column of the Royal Horse Artillery on the Western Front, where he gained a reputation as an outstanding planner of operations.

[15] At the Battle of the Somme in 1916, he introduced the French "creeping barrage" system, thereby helping the protection of the advancing infantry from enemy machine gun fire.

[29] Brooke correctly predicted that the Allied powers' Plan D envisioning an advance along the Meuse would allow the Wehrmacht to outflank them, but British High Command dismissed his warnings as defeatist.

[30] When the German offensive began, Brooke, aided by Neil Ritchie, his Brigadier General Staff (BGS), distinguished himself in the handling of the British forces in the retreat to Dunkirk.

[31] Brooke's actions not only saved his own forces from capitulation, but prevented the Germans from seizing the 20-mile gap left by the Belgian surrender and capturing the entire BEF before it could safely evacuate.

After General Maxime Weygand warned him that the French Army was collapsing and could offer no further resistance, he decided that he needed to convince his superiors to allow him to withdraw his forces to Cherbourg and Brest for evacuation to Britain.

[33] In his first conversation with Prime Minister Winston Churchill (Brooke had been rung by Dill who was at 10 Downing Street) he insisted that all British forces should be withdrawn from France.

Contrary to his predecessor General Sir Edmund Ironside, who favoured a static coastal defence, Brooke developed a mobile reserve which was to swiftly counterattack the enemy forces before they were established.

[44] Brooke was responsible for commanding the entire British Army; he focused on grand strategy, and his relationships, through the Combined Chiefs of Staff, with his American counterparts.

In addition he had primary responsibility for supervising the military operations of the Free French, Polish, Dutch, Belgian, and Czech units reporting to their governments in exile in London.

[46] Brooke's and the British view of the Mediterranean operations contrasted with the American commitment to an early invasion of western Europe, which led to several heated arguments at the many conferences of the Combined Chiefs of Staff.

At the London Conference in April 1942, Brooke and Churchill seem to have misled General George C. Marshall, the U.S. Army Chief of Staff, about the British intentions on an early landing in France.

At the Casablanca Conference in January 1943, it was decided that the Allies should invade Sicily, under the command of General Dwight D. Eisenhower, a decision that effectively postponed the planned invasion of Western Europe until 1944.

[55] According to historian Max Hastings, Brooke's reputation as a strategist was "significantly damaged" by his remarks at the Trident Conference in Washington in May 1943, where he claimed that no major operations on the continent would be possible until 1945 or 1946.

[56] His diary says that he wanted "operations in the Mediterranean to force a dispersal of German forces, help Russia, and thus eventually produce a situation where cross Channel operations are possible" but that Churchill "entirely repudiated" (or half repudiated) the paper we (the CCOS) had agreed on; Harry Hopkins got him to withdraw his proposed amendments but that Churchill had aroused suspicions with his talk of "ventures in the Balkans.

"[58] Shortly after the Japanese attack on Pearl Harbor, Churchill and his senior military staff used the Arcadia Conference in Washington to decide the general strategy for the war.

[59] When Churchill's many fanciful strategic ideas collided with sound military strategy it was only Brooke on the Chiefs of Staff Committee who was able to stand up to the Prime Minister.

The CIGS was sceptical about the British intervention in the Greek Civil War in late 1944 (during the Dekemvriana), believing this was an operation which would drain troops from the central front in Germany.

After one fierce clash Churchill told his chief of staff and military adviser, General Sir Hastings Ismay, that he did not think he could continue to work any longer with Brooke because "he hates me.

According to historian Max Hastings, their partnership "created the most efficient machine for the higher direction of the war possessed by any combatant nation, even if its judgments were sometimes flawed and its ability to enforce its wishes increasingly constrained".

Among the few individuals of whom Brooke seems to have kept consistently positive opinions, from a military standpoint, were General of the Army Douglas MacArthur,[72] Field Marshal Sir John Dill, and Joseph Stalin.

Otherwise he had no illusions about the man, describing Stalin thus: "He has got an unpleasantly cold, crafty, dead face, and whenever I look at him I can imagine his sending off people to their doom without ever turning a hair.

Originally Brooke intended that the diaries were never to be published but one reason that he changed his mind was the lack of credit to him and the Chiefs of Staff in Churchill's own war memoirs, which essentially presented their ideas and innovations as the Prime Minister's own.

Although censorship and libel laws accounted for numerous suppressions of what Brooke had originally written concerning persons who were still alive, the Bryant books became controversial even in their truncated state, mainly as a result of the comments on Churchill, Marshall, Eisenhower, Gort, and others.

[75][70] In 1952, both Churchill and Beaverbrook threatened legal action against a biography of Stanley Baldwin by G. M. Young, and a settlement was reached by lawyer Arnold Goodman to remove the offending sentences.

Danchev and Todman also criticised Bryant's editing, but this is balanced by an assessment by Dr Christopher Harmon, advisor to the Churchill Centre and Professor at the US Marine Corps University.

[78][79] Following the Second World War and his retirement from the regular army, Lord Alanbrooke, as he was now, who could have chosen almost any honorary position he wanted, chose to be the Colonel Commandant of the Honourable Artillery Company.

The couple had one daughter and one son: Jane Brooke died of complications from an operation to repair a broken vertebra following a car accident in 1925 in which her husband was at the steering wheel.

He is memorably described by the narrator in Anthony Powell's novel, The Military Philosophers (the 9th volume in his roman-fleuve, A Dance to the Music of Time), who refers to:[131]...the hurricane-like imminence of a thickset general, obviously of high rank, wearing enormous horn-rimmed spectacles.