Joe Kloc in The Daily Dot:
Before the NSA came to life on the eve of Dwight Eisenhower's election, its job was done by a loose group of three independent intelligence outfits in the Army, Navy, and Air Force. The groups came into their own during World War II, as Washington began to see that significant signals intelligence, or SIGINT, could be invaluable in wartime: On the Western front, British cryptographer Alan Turing’s Enigma machine had been able to decode German movements during the Allied forces invasion of Normandy. On the Pacific front, U.S. intelligence became so crucial that Admiral Chester Nimitz said SIGINT deserved credit for the Allied victory during the Battle of Midway.
But just as the American SIGINT program’s successes came into focus during the war, so did its weaknesses. The three groups, two of which were run out of separate, converted women's schools, often viewed one another as competitors. At one point, the Army and Navy went so far as to divide up intelligence work based on whether the day of the month was odd or even. (NSA historian Thomas Johnson would describe this peculiar practice as a “Solomonic Solution.”) The British government—in many ways superior in those days in terms of intelligence gathering—would later liken dealing with the American intelligence community to dealing with the colonies after the Revolutionary War.