How far back do you want to go?

"The LORD spoke to Moses: 2 "Send men to scout out the land of Canaan I am giving to O the Israelites." (Numbers 10)

Scipio brought centurians disguised as slaves with a delegation into Hannibals camp to collect information so the Romans could plan an attack.

Walsingham, Queen Elizabeth's spy master planned and executed some baroque operations against the Papal States and Mary, Queen of Scots.

George Washington managed a fairly complex network of spys through the American Revolution.

The Pinkertons during the Southern Insurgency/War of Northern Aggression are a case study in outsourcing intelligence.

Baden Powell, founder of the Boy Scouts, reconned the Balkans prior to WW I.

For counter intelligence, in ancient Greece, Rhodes had laws expressly forbidding foreigners from going to their shipyards. (Dr. R. Rice, a naval history would be the place to search for more on this.)

Immediately prior to the Peloponnsian War, the tyrannt of Athens locked down the Spartan delegation so they couldn't report before he presented his case to the Spartan assembly.

We could go on, but what era or region is most interesting to you?