OVERVIEW

ADDRESS: St. John's College, Cambridge CB2 1TN ENGLAND.

ABSTRACT: During World War II, signals intelligence was always and increasingly the most valuable of Great Britain's intelligence sources. The Poles first solved the German Enigma cipher machine. Britain, which first solved the general Luftwaffe key in May 1940 and a naval Enigma key in June 1941, exploited these and other keys, though with interruptions, to the end of the war. Other sources - espionage, aerial photography, captured documents, the underground in occupied countries - also provided valuable information. The operational influence of intelligence varied. After the summer of 1941, most battles were influenced by Allied superiority in intelligence. But its impact was not always decisive. Intelligence alone did not win the war. Still, massive, continuous, and frequently current information enabled the Allies to speed their victory by setting the time, scale, and place of their operations so as to economize their lives and resources and to cost the enemy more of his. Intelligence shortened the war by perhaps 4 years.

KEYWORDS: Second World War, intelligence, signals intelligence, Ultra, Enigma, Poles, U-boats.

In the Second World War, if we leave aside the information they obtained by overt means from embassies, the press, the radio and other such channels - information which they did not call intelligence - governments got their intelligence - defined as information which other governments were at pains to keep secret -from four sources. They were:

1. physical contact in the form of captured documents, the...