The changing nature of warfare and international conflict, 1919–2011 — timeline

Key topic 1 · The changing nature of warfare, 1919–39

Gas, tanks, artillery, submarines and aircraft between the wars

1925

The Geneva Protocol prohibits the use in war of asphyxiating gases and bacteriological methods. Why this date: It bans USE and not possession or manufacture, which is exactly why every power kept stockpiles and why the ban held by deterrence rather than by law.

1935–36

Italy invades Abyssinia, using aircraft and mustard gas against troops and civilians. Why this date: The first demonstration that a signatory would break the Protocol against an opponent unable to retaliate, which is the condition the whole ban turned on.

1937

Japanese air attacks on Chinese cities during the invasion of China. Why this date: It supplied European planners with their picture of what bombing a city does, before anybody had tried it against defended airspace.

Guerrilla tactics in the Spanish Civil War

July 1936

The military rising against the Republic begins; militias rather than armies hold the early lines. Why this date: It explains why irregular methods were available at all — there was no continuous professional front to prevent them.

26 April 1937

Guernica is bombed by the Condor Legion. Why this date: It is the event European air staffs used as evidence, so it shapes 1939–40 planning far more than it shaped the Spanish war.

April 1938

Nationalist forces reach the Mediterranean and cut the Republic in two. Why this date: A conventional operation decides the war, which is the evidence against reading Spain as a guerrilla victory of any kind.

Key topic 2 · Changing methods of warfare by land, air and sea, 1939–45

Blitzkrieg, the Battle of Britain, the Blitz and the bomber offensive

10 May – 22 June 1940

The German offensive in the west; France signs an armistice. Why this date: Six weeks against four years in 1914–18, with broadly the same weapons, is the sharpest evidence for doctrinal rather than technological change.

July – October 1940

The Battle of Britain; the German air force fails to gain air superiority. Why this date: The first defeat of the method, and the first evidence that an integrated defence system beats numbers.

July 1943

The bombing of Hamburg produces a firestorm. Why this date: It marks the point at which area bombing achieved its intended destructive effect, which sharpens rather than settles the argument about results.

1944–45

V-1 and V-2 attacks on Britain and Belgium. Why this date: The V-2 is the first ballistic missile used in war and could not be intercepted, so its significance is post-war rather than wartime.

U-boats, amphibious operations and aircraft carriers

7 and 10 December 1941

Pearl Harbor, and the sinking of Prince of Wales and Repulse at sea by aircraft. Why this date: The second event removes the excuse available for the first: these ships were at sea and manoeuvring, and aircraft sank them anyway.

June 1942

Midway: four Japanese fleet carriers lost. Why this date: It ends Japanese offensive capability in the central Pacific and confirms that carrier air, not gunnery, decides fleet actions.

May 1943

Dönitz withdraws the U-boats from the North Atlantic after losing 41 in the month. Why this date: It is the moment the sea lanes become secure, and therefore the moment a cross-Channel invasion becomes schedulable.

6 June 1944

The Normandy landings. Why this date: It demonstrates that a defended coast can be assaulted successfully, overturning the conclusion drawn from Gallipoli in 1915.

Key topic 3 · New forms of conflict – nuclear and guerrilla war versus conventional war, 1945–75

The decision to drop the atomic bombs

16 July 1945

The Trinity test in New Mexico. Why this date: It is the first moment at which the weapon was a fact rather than a hope, and it falls during the Potsdam Conference.

6 August 1945

Hiroshima. Why this date: The first use, and the point from which every argument about deterrence in the rest of this option runs.

8 August 1945

The Soviet Union declares war on Japan and invades Manchuria. Why this date: It falls between the two bombs, which is why the causes of the Japanese surrender cannot be settled by naming Hiroshima alone.

9 August 1945

Nagasaki. Why this date: The second use, three days later, is what makes the question of why twice examinable.

15 August 1945

The Japanese surrender is announced. Why this date: It dates the outcome the decision was meant to produce, six days after the second bomb.

The arms race, MAD and proliferation

August 1949

The first Soviet atomic test ends the American monopoly. Why this date: It converts a one-sided weapon into a relationship, which is the precondition for everything called deterrence afterwards.

1952 and 1953

American and Soviet thermonuclear tests. Why this date: The jump in yield removes the possibility of treating nuclear weapons as very large conventional ones.

1968

The Non-Proliferation Treaty is opened for signature. Why this date: It fixes the distinction between states that had tested by 1967 and everybody else, which is the structure of the proliferation argument ever since.

1972

SALT I and the ABM Treaty are signed. Why this date: They cap launchers and limit defences while leaving multiple warheads per missile alone, which is why warhead numbers rose during arms control.

Conventional and guerrilla war, 1945–75

June 1967

The Six-Day War: Israeli air strikes destroy Arab air forces on the ground, followed by an armoured campaign. Why this date: It is the clearest demonstration that high-intensity conventional war persisted, and that air superiority obtained in hours could decide a land campaign.

January 1968

The Tet Offensive. Why this date: It separates military outcome from political effect more sharply than any other event on this option, which is the core of asymmetric warfare.

October 1973

The Yom Kippur War: anti-tank and surface-to-air missiles inflict heavy losses on armour and aircraft. Why this date: It forces the refinement of combined arms rather than the abandonment of armour, which is the more accurate lesson.

1973 and 1975

American forces withdraw; Saigon falls. Why this date: It dates the outcome and shows the two-year gap between withdrawal and collapse, which candidates often merge.

Key topic 4 · Conventional war and the development of 'new' wars, 1976–2000

The first Gulf War, the Falklands and carrier warfare

2 May 1982

HMS Conqueror sinks the General Belgrano; the Argentine surface fleet returns to port. Why this date: It shows a nuclear submarine removing a navy from a campaign by threat rather than by sustained attrition.

4 May 1982

HMS Sheffield is hit by an Exocet missile. Why this date: It is the moment the anti-ship missile's threat to surface fleets became undeniable, and it reshaped naval air-defence procurement.

17 January 1991

The coalition air campaign against Iraq begins. Why this date: Five weeks of air attack before any ground assault is the structural fact of the campaign.

24–28 February 1991

The ground offensive: about a hundred hours. Why this date: The contrast between five weeks and a hundred hours is the evidence for the claim that air power shortened rather than replaced the land battle.

Afghanistan, 'Star Wars' and the end of the arms race

December 1979

Soviet forces enter Afghanistan. Why this date: It begins the nine-year commitment whose failure supplies the Vietnam parallel and the pressure on the Soviet system.

March 1983

The Strategic Defense Initiative is announced. Why this date: It challenges the logic of the ABM Treaty and therefore the stability of deterrence, which is why it dominated the arms talks that followed.

1986

Stinger missiles reach the Afghan resistance in quantity. Why this date: It restricts Soviet helicopter operations, which had been the answer to a country with few usable roads.

December 1987

The INF Treaty is signed. Why this date: It is the first agreement to eliminate a class of weapons with on-site verification, which is reduction rather than limitation.

February 1989

The Soviet withdrawal from Afghanistan is completed. Why this date: It dates the failure and falls in the same year as the collapse of Soviet control in Eastern Europe.

Key topic 5 · Changing methods of warfare at the beginning of the 21st century, 2000–2011

Terrorism, 'surgical' strikes and unmanned systems

11 September 2001

Attacks on New York and Washington kill almost three thousand people. Why this date: It is the point at which a non-state network produced a strategic effect previously available only to states, which is what reorients policy.

October 2001

Intervention in Afghanistan begins. Why this date: It starts a campaign that outlasts this specification's period and shows the limits of high-technology force against dispersed opponents.

2003

The invasion of Iraq. Why this date: A conventional campaign won quickly is followed by an insurgency, which is the clearest instance of the difference between defeating an army and controlling a country.

2004–11

Drone strikes in Pakistan expand substantially. Why this date: It marks the arrival of routine armed action outside any declared war, which is the change of category this key topic is about.