Two years after World War I broke out, William Schlemmer Sr. dies at the age of 75, leaving his son William F. Schlemmer complete control of the company. Schlemmer was remembered as "an indefatigable worker, and a man of the highest possible character, whose habits were exemplary in the extreme, and whose business principles were beyond reproach."
In 1918, after the war had ended, Hammacher Schlemmer is commended for its service to munitions factories during the war. The firm receives a citation that read: "The War Department of the United States of America recognizes in this award for distinguished service the loyalty, energy and efficiency in the performance of the war work by which Hammacher Schlemmer Co. added materially in obtaining victory for the arms of the United States of America in the war with the Imperial German Government and the Imperial and Royal Austro-Hungarian Government."
The assassination of Archduke Franz Ferdinand, the heir to the Austro-Hungarian throne, sparks World War I, or the Great War. In less than a month, much of Europe is engulfed in war with the Entente Powers-France, the United Kingdom, Russia, and later, Italy and the United States-on one side and the Central Powers-Germany, Austria-Hungary, Bulgaria, and the Ottoman Empire-on the other. On November 11, 1918, the Entente Powers signed an armistice with the Central Powers, ending a war which killed over 8 million and signaled the end of four empires-the German, Austro-Hungarian, Ottoman, and Russian.
During the Russian revolution, the Czar sent an emissary to New York City to buy the world's greatest hardware and supplies. The representative from Russia reportedly asked for "A lot of everything."
According to a Hammacher Schlemmer magazine ad, "There is nothing more fascinating to the average man or boy than Tinkering With Tools". An oak cabinet that transformed into a tool bench with vise when opened could be purchased with as many as 95 tools "for the man who is really handy" or as few as 21 tools "for one less expert, or for the boy".