21. The troop movement rumors may have contributed to the sinking
In late April, 1917, as Lusitania took on its cargo in New York and prepared for its final crossing, German intelligence in Berlin began receiving information regarding movement of troops from Canada and Ireland to Great Britain. The troops were to be assembled, equipped, and transferred to the Western Front in Flanders and France. U-Boats were dispatched by the Imperial Navy, U-20 being one of them. The submarines were to watch the Irish ports, Liverpool, and the approaches from the west, specifically for troopships. Lusitania had not been used for transporting troops, but other liners had, and would again later in the war.
The rumors were just that, and whether they were part of a deliberate disinformation campaign has never been proven. The U-Boats were dispatched. U-20 actually attacked, or rather attempted to attack, another liner, White Star’s Arabic, before the attack on Lusitania (Arabic was sunk by U-24 in August, 1915, causing another diplomatic incident). What is known is that after U-20 sailed, it received transmissions which changed its orders.