During the expansion of the British Empire, spearheaded by British military forces that included Highland regiments, the Scottish Great Highland bagpipe became well known worldwide. This surge in popularity was boosted by large numbers of pipers trained for military service in World War I and World War II. The surge coincided with a decline in the popularity of many traditional forms of bagpipe throughout Europe, which began to be displaced by instruments from the classical tradition and later by gramophone and radio.