How do you guerrilla advertise to guerrilla fighters?

(via)
Skywriting? Dud mortal shells with messages inside (OPEN ME! on the outside)?
The Colombian government enlisted their ad agency, Bogota's Lowe SSP3, to try and entice the FARC guerrillas to disarm and come home to their families for Christmas. Lowe created Operation Rivers of Light—floating plastic balls filled with messages and small gifts from family and friends down waterways used by the insurgents.
"We had overlooked that the highways of the jungle are the rivers," said Jose Miguel Sokoloff, chief creative officer of the Lowe agency.
The balls are equipped with LEDs that recharge on solar power and will remain lighted for about two weeks, according to Mr. Sokoloff. They will be placed in nine different rivers, one in each of the areas still occupied by guerrillas. The first wave of about 1,000 balls has been sent down two rivers. An estimated 4,000 to 5,000 fighters are believed left, Mr. Sokoloff said, vs. as many as 30,000 a decade ago. The outreach encourages them to defect from their camps and surrender to Colombian soldiers, who have been instructed not to harm them (right).
Interesting. But it seems like more of a PR ploy than an olive branch. Video below.
See more creative guerrilla advertising here.