The phrase "Loose Lips Sink Ships" is one of the most recognized slogans of World War II, but it was rooted in genuine security concerns. In the early war years, German intelligence gathered valuable information from casual conversations by merchant sailors and military personnel in port cities. Bars, restaurants, and boarding houses near naval bases were monitored.
In one documented case, a sailor mentioned his convoy's departure date in a New York bar; the convoy suffered unusually heavy losses to U-boats. While direct cause-and-effect was difficult to prove conclusively, naval intelligence identified numerous instances where ship movement details discussed in public correlated with subsequent attacks.
The War Advertising Council created a series of posters with increasingly dramatic imagery: drowning sailors, sinking ships, and menacing figures listening from the shadows. Other memorable variants included "Someone Talked!" and "The Enemy Is Listening." The campaign fundamentally changed American attitudes about casual conversation regarding military matters.