WORLD HISTORY

Detailed explanation-1: -It was this action that technically caused the British to enter the war, as they were still bound by the 1839 agreement to protect Belgium in the event of war.

Detailed explanation-2: -Germany, as part of a massive attack on France, invaded northern France through Belgium early on the morning of 4 August. The Belgians called upon Britain for military assistance under the 1839 treaty, and in response London gave Berlin an ultimatum which expired at 11 pm London time, which was ignored.

Detailed explanation-3: -So what caused Britain to enter the Great War? The British came in partly because of Belgium, a neutral state when Germany invaded it (and Luxembourg) as part of the Schlieffen Plan at the start of World War One.

Detailed explanation-4: -Germany declared war on France. To avoid the French fortifications along the French-German border, the troops had to cross Belgium and attack the French Army by the north. Of course, Belgians refused to let them through, so the Germans decided to enter by force and invaded Belgium on Aug. 4, 1914.

Detailed explanation-5: -Belgium, a neutral state, was forced into the First World War by a German ultimatum, a fact with considerable international resonance. The war had a deep impact on what was, in 1914, the most densely-populated country in the world.