Espionage: Definition, History, Acts & Techniques

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  • 0:03 What Is Espionage?
  • 0:53 History
  • 2:28 Espionage Act of 1917
  • 3:14 Espionage Techniques
  • 4:50 Lesson Summary
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Lesson Transcript
Instructor: Janell Blanco
We've all heard the term espionage, but do we really know what it is? This lesson not only defines espionage, but also discusses the history of espionage and looks at some of the many techniques of espionage.

What Is Espionage?

''One if by land, and two if by sea.'' Does this ring a bell? Have you heard of or read the poem ''Paul Revere's Ride'' by Henry Wadsworth Longfellow?

Well, Paul Revere was a spy. He spent time eavesdropping on the British military to see how they would attack John Hancock and his men in Lexington. One lantern meant they were coming by land and two lanterns meant they were coming by sea. Pretty sneaky, right?. What Paul Revere did is espionage. But, what really is espionage?

Let's put this in the easiest terms as possible. Spies, as you probably already know, are individuals who illegally take the secrets or confidential information from their enemies. The actual act of obtaining and then passing on illegally obtained confidential or secret information is espionage.


Spies have been around since the start of time. There are even mentions of spies in the Bible.

During the Revolutionary War, the Americans had double agents, or spies that are working for both parties but are actually only loyal to one side. Double agents take the secrets of the enemy side and report back to the side to which they are loyal. During the Revolutionary War, General George Washington saw a need to combat espionage. He used one of the earliest known espionage techniques of feeding wrong information to the other side to fake them out. He also asked Congress for funding for intelligence operations, and Congress obliged (about two years after his request).

The Civil War introduced the use of hot air balloons as an espionage technique to spy on troop movements. World War I was difficult on the Americans as they lost their budget to gather intelligence. They had to rely on the troops to gather intelligences and on the Secret Service, the New York Police Department, and military counterintelligence to squash espionage within the United States. The focus became on decoding messages, which resulted in the arrests of several foreign agents that were in the U.S.

WWII was a tough time for the U.S.'s quests to sabotage espionage efforts as Japan bombed Pearl Harbor. The U.S. intelligence agents were not able to intercept this information due to a multitude of errors. In 1942, shortly after the bombing of Pearl Harbor, the Central Intelligence Agency (CIA) became responsible for gaining information and intelligence about the enemy as well as combating espionage within the U.S.

Espionage Act of 1917

Now that we know the history of espionage in the U.S., let's take a look at the Espionage Act of 1917.

In June of 1917, the Espionage Act was passed. While there are many facets to this act, simply put, the Espionage Act made spying against the U.S. an illegal act punishable by up to 20 years in prison and a fine of up to $10,000. Concerned with our entry into World War I, the act was put into place to help fight against spies, espionage, and the threat of U.S. secrets getting into the hands of the wrong people. Under this act, postmasters were also given the permission to withhold mail that that was treasonable or seditious. Treason is the act of betraying your own country by providing secrets or intelligence to another country.

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