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

What a Grade 9 answer knows here. Every weapon of the Second World War existed by 1918. The interwar change is doctrinal, not technological: the argument about what tanks and aircraft are FOR is what separates 1940 from 1918.

Every lesson here ends the same way: learn it, teach it to an AI pupil who asks the awkward question, then defend it against the thinker with the strongest claim on it — free · no account needed.

2 lessons, each answering one essential question with the story, the dates that earn marks, the people to place, how historians disagree and the cap in the mark scheme that bites. Completely free.

The 2 lessons

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

If every weapon of the Second World War already existed in 1918, what actually changed by 1939? The armies that demobilised in 1919 owned tanks, aircraft, submarines, chemical weapons and artillery capable of firing a million shells in a week.

Examined through continuity and change. Learn gas, tanks, artillery, submarines and aircraft between the wars →

Guerrilla tactics in the Spanish Civil War

What did Europe's armies learn from Spain, and what did they take away that was not true? The Spanish Civil War began in July 1936 when part of the Spanish army rose against the elected Republican government.

Examined through change and significance. Learn guerrilla tactics in the Spanish Civil War →

The dates that earn marks in this key topic

Two from each lesson, in the order the topic is taught — each with the reason it is worth a mark, and the lesson that places it.

1925 — The Geneva Protocol prohibits the use in war of asphyxiating gases and bacteriological methods.: 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. (Gas, tanks, artillery, submarines and aircraft between the wars)
1935–36 — Italy invades Abyssinia, using aircraft and mustard gas against troops and civilians.: 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. (Gas, tanks, artillery, submarines and aircraft between the wars)
July 1936 — The military rising against the Republic begins; militias rather than armies hold the early lines.: It explains why irregular methods were available at all — there was no continuous professional front to prevent them. (Guerrilla tactics in the Spanish Civil War)
26 April 1937 — Guernica is bombed by the Condor Legion.: It is the event European air staffs used as evidence, so it shapes 1939–40 planning far more than it shaped the Spanish war. (Guerrilla tactics in the Spanish Civil War)

The people to place

J. F. C. Fuller — British officer and theorist of concentrated independent armoured formations. (Gas, tanks, artillery, submarines and aircraft between the wars)
Giulio Douhet — Italian officer whose case for strategic bombing shaped interwar air budgets across Europe. (Gas, tanks, artillery, submarines and aircraft between the wars)
Francisco Franco — Commander of the Nationalist forces and, from 1939, ruler of Spain. (Guerrilla tactics in the Spanish Civil War)
Hugo Sperrle — First commander of the German Condor Legion, the force whose aircraft bombed Guernica. (Guerrilla tactics in the Spanish Civil War)

What students say — and what is actually the case

“Blitzkrieg was made possible by German technology that nobody else had.” — French tanks in 1940 were in several respects better armed and armoured than German ones. What Germany had was concentration, radio in every vehicle, and air support trained to work with ground formations. (Gas, tanks, artillery, submarines and aircraft between the wars)
“Guerrilla warfare won or nearly won the Spanish Civil War.” — The war was decided by conventional operations: the capture of the north, the Ebro campaign and the drive to the sea in April 1938. Irregular action was real and secondary. (Guerrilla tactics in the Spanish Civil War)

What the specification asks for

The clauses of 4HI1 this key topic examines, one per lesson. Incandio is aligned to the specification and is not published by Pearson.

“Changes in the nature of warfare, including gas, tanks and heavy artillery. Emergence of submarines and military aircraft – fighter and bomber planes in conflicts in East Asia and Abyssinia.” — Gas, tanks, artillery, submarines and aircraft between the wars
“Use of guerrilla tactics in the Spanish Civil War.” — Guerrilla tactics in the Spanish Civil War

Then teach it, and defend it

Every lesson above ends the same way: you explain the argument to Ember, an AI pupil who asks the awkward question, and defend it in a structured debate marked against published descriptors.

All of The changing nature of warfare and international conflict, 1919–2011 · Incandio History · The 4HI1 specification