1217 CE
A year marked by the launch of the Fifth Crusade toward Egypt and the resolution of the First Barons' War in England.
Conflict & Security
- The Fifth Crusade was launched with forces gathering at Acre in the Holy Land, with the strategic aim of conquering Egypt as a stepping stone to recapturing Jerusalem.
- The First Barons' War in England ended with the defeat of rebel barons and their French allies at the Battle of Lincoln in May and the naval Battle of Sandwich in August.
- The young King Henry III of England, aged nine, secured his throne after the regent William Marshal led royalist forces to decisive victories against the French invaders and rebel barons.
Geopolitics & Diplomacy
- The Treaty of Lambeth in September ended the French intervention in England, with Prince Louis abandoning his claim to the English throne and withdrawing his forces.
Climate & Environment
- Atmospheric carbon dioxide concentration was approximately 275 parts per million, as later confirmed by ice core analysis.
Culture & Society
- The estimated world population was approximately 369 million.