None. All German spies were captured before they had a chance to start operating.
they spied on their enemy
Not quite sure of the question? But, all sides in the world wars had spies reporting back important information of an enemy's activities, from deep within the enemies camp.
The FBI and Army and Navy counterintelligence agents and OSS agents spied on the spies to prevent them from gathering info
to find out enemy's plans and seek other information
Chapter 13 of the Art of War is all about spies. Sun Tzu thought that using spies to gain information, either your own or by getting enemy spies to give up information was an important part of a war effort.
In general, scouts determine the current disposition and movement of enemy troops, spies infiltrate enemy lines and use every possible means to gather useful information.
They would date enemy soldiers to get information
Spies were utilized by many nations to gather intelligence against the enemy.
They used disguises of the enemy, as in... American Spies wear German Clothing Itailan Spies wear French Clothing Spies in World War 2 were more like "moles" than spies. A "mole" is like a spy, but they work for both sides, but provide info and really work for only one side.
During World War 1, there were hundreds of German spies who were caught in the United Kingdom. They were all killed upon captivity.
Spies
Spies were paid during the American Revolution. Spies were paid for information and most of the their information didn't come cheaply.