Remembrance Day (sometimes known informally as Poppy Day) is a memorial day observed in Commonwealth of Nations member states since the end of the First World War to remember the members of their armed forces who have died in the line of duty. Following a tradition inaugurated by King George V in 1919, the day is also marked by war remembrances in many non-Commonwealth countries. Remembrance Day is observed on 11 November in most countries to recall the end of hostilities of World War I on that date in 1918. Hostilities formally ended "at the 11th hour of the 11th day of the 11th month", in accordance with the armistice signed by representatives of Germany and the Entente between 5:12 and 5:20 that morning. ("At the 11th hour" refers to the passing of the 11th hour, or 11:00 am.) The First World War officially ended with the signing of the Treaty of Versailles on 28 June 1919.
The memorial evolved out of Armistice Day, which continues to be marked on the same date. The initial Armistice Day was observed at Buckingham Palace, commencing with King George V hosting a "Banquet in Honour of the President of the French Republic" during the evening hours of 10 November 1919. The first official Armistice Day was subsequently held on the grounds of Buckingham Palace the following morning.
The red remembrance poppy has become a familiar emblem of Remembrance Day due to the poem "In Flanders Fields" written by Canadian physician Lieutenant-Colonel John McCrae. After reading the poem, Moina Michael, a professor at the University of Georgia, wrote the poem, "We Shall Keep the Faith," and swore to wear a red poppy on the anniversary. The custom spread to Europe and the countries of the British Empire and Commonwealth within three years. Madame Anne E. Guerin tirelessly promoted the practice in Europe and the British Empire. In the UK Major George Howson fostered the cause with the support of General Haig. Poppies were worn for the first time at the 1921 anniversary ceremony. At first real poppies were worn. These poppies bloomed across some of the worst battlefields of Flanders in World War I; their brilliant red colour became a symbol for the blood spilled in the war. Wikipedia