Cunard Line is a British-American-owned British-operated shipping company that has been a leading operator of passenger ships on the North Atlantic for over a century. In 1839, Canadian-born Samuel Cunard was awarded the first British transatlantic steamship mail contract, and the next year formed the British and North American Royal Mail Steam-Packet Company to operate the line's four pioneer paddle steamers on the Liverpool–Halifax–Boston route. For most of the next 30 years Cunarders held the Blue Riband for the fastest Atlantic voyage. However, in the 1870s Cunard fell behind its rivals, the White Star Line and the Inman Line. To meet this competition, in 1879 the firm was reorganized as Cunard Steamship Company, Ltd to raise capital.
SS Imperator was an ocean liner built for the Hamburg America Line (German: Hamburg-Amerikanische Packetfahrt-Actien-Gesellschaft or HAPAG) launched in 1912. She was the first of a trio of successively larger Hamburg America ships that included SS Vaterland and SS Bismarck built by the line for transatlantic passenger service. At the time of her launch in May 1912, she was the largest passenger ship in the world superseding the sunken RMS Titanic. During World War I, the ship remained in port in Hamburg. After the war she was briefly commissioned into the United States Navy as USS Imperator (ID-4080) and employed for returning American troops from Europe. Following her U.S. Navy service, Imperator was handed over to Britain's Cunard Line as part of war reparations, and she sailed as the flagship RMS Berengaria for the final decade of her career.