In this fascinating book, Ian Kershaw narrates how ten decisions, crucial for the outcome of World War II but also with broader consequences for the post-war world, were made between May 1940, when Britain chose to fight rather than surrender, and the autumn of 1941, when Hitler decided to exterminate the Jews.

In London, Tokyo, Rome, Berlin, and Washington, a series of politicians and generals, often with insufficient information and facing enormous difficulties on economic, logistical, and military levels, had to decide how to utilize or attempt to stem the ever-growing crisis. These decisions indeed changed the world. The book offers the reader a realistic picture of the constraints these leaders had to face, as well as the role of personality: Churchill continues the fight despite the disaster in France, Hitler orders an invasion of the USSR despite Germany's failure to defeat the British, Stalin trusts Hitler and leaves his country defenseless, Japanese generals decide to strike the US despite indications that it would lead to defeat.

The choices narrated and commented on by the author are as follows:
- London, spring 1940 - Great Britain decides to continue the fight
- Berlin, summer and autumn 1940 - Hitler decides to attack the Soviet Union
- Tokyo, summer and autumn 1940 - Japan decides to seize the "golden opportunity"
- Rome, summer and autumn 1940 - Mussolini decides to grab his share
- Washington, summer 1940-spring 1941 - Roosevelt decides to lend a hand
- Moscow, spring-summer 1941 - Stalin decides that he knows best
- Washington, summer-autumn 1941 - Roosevelt decides to wage an undeclared war
- Tokyo, autumn 1941 - Japan decides to go to war
- Berlin, autumn 1941 - Hitler decides to declare war on the United States
- Berlin/East Prussia, summer-autumn 1941 - Hitler decides to kill the Jews