UK Citizenship Practice Test 2025 - Free Citizenship Practice Questions and Study Guide

The event that marks the start of the Second World War in 1939 is the invasion of Poland. On September 1, 1939, Nazi Germany invaded Poland, which prompted Britain and France to declare war on Germany soon after, marking the official beginning of the conflict. This invasion violated several international agreements and was a key strategic move by Adolf Hitler to expand German territory and influence, leading to the outbreak of war across Europe.

The other events mentioned, such as the bombing of Pearl Harbor, which occurred in 1941, relate to the involvement of the United States in the war rather than its start. The signing of the Treaty of Versailles in 1919 was an agreement that ended the First World War and imposed restrictions on Germany, which contributed to the conditions that led to the Second World War but did not initiate it. The D-Day landings happened in 1944 and were part of a significant Allied offensive against German-held territory in France during the war, far removed from the initial trigger that set the war in motion.