After Karl Baedeker died, his son, also named Karl, inherited the Baedeker travel guide business; however, he was killed in action during World War I. British nationalism and anti-German sentiment resulted in some British people labeling Baedeker guides "instrumental to the German war effort", and their popularity in the United Kingdom dropped considerably. As a result, the two editors of Baedeker's English-language titles left the company and acquired the rights to Murray's Handbooks. The resulting guide books, called the Blue Guides to distinguish them from the red-covered Baedekers, constituted one of the major guide book series for much of the 20th century and are still published today.