How did the phrase 'Loose Lips Sink Ships' originate?

This phrase ('Loose Lips Sink Ships') was coined as a slogan during World War II. It was created by the War Advertising Council, Inc. and used on posters as part of the U.S. Office of War Information's attempt to limit the possibility of people inadvertently giving useful information to enemy spies. At first the slogan was actually 'Loose Lips Might Sink Ships'. It was changed.

The phrase was one of several similar slogans such as 'Defense On The Sea Begins On The Shore', 'Defense In The Field Begins In The Factory', etc. They all came under the campaigns basic message - 'Careless Talk Costs Lives'. Everyone in the country tried to eliminate unguarded talk. No one wanted to give any useful information to the enemies of the United States and its Allies.

Informative posters were then widely used in many propaganda campaigns. Their content ranged from simple instructions like 'Loose Lips Sink Ships' to purely motivational content which encouraged people to volunteer for onerous or dangerous war work in factories or the nation's military.