I can see you

In his work on the evil eye, folklorist Alan Dundes wrote about the powerful effect of blue glass eyes-of-God one sees throughout the Arabic world, hanging in houses, and eyes painted on shopfronts to scare away petty thieves.

Back in the day when the CIA was the OverSeas Service (OSS), they recruited folks who also read folklore:

Another of Lansdale's spooky counterinsurgency tricks was what he called the "eye of God technique," wherein government troops, using information gathered from counterintelligence efforts, called out the names of Huk guerrillas over loudspeakers and threatened the rebels with death if they did not surrender.

Lansdale devised a related scheme to intimidate civilians, using "all-seeing eye" graffiti to threaten constant surveillance. He later wrote:

"[the method] was especially useful in towns where some of the inhabitants were known to be helping the Huks secretly. The army would warn these people that they were under suspicion.

At night, when the town was asleep, a psywar team would creep into town and paint an eye on a wall facing the house of each suspect.

The mysterious presence of these malevolent eyes the next morning had a sharply sobering effect.

-- Jon Elliston on Pscyhological Operations in War, interesting history from the conspiracy nuts