As drill sergeant for a guerrilla group that was wiped out by the MSF, sole survivor and captive Kazuhira Miller wanted a "contest" to either win his freedom or join the MSF. Miller arranged for Miel to deliver a letter to his reserve guerrillas (who weren't present at the battle) as a trump card against Big Boss. Miel delivered the letter to the guerillas, who responded that "the operation was a go," with the signal to emerge being when he loudly declared "speed shooting" toward sunset. Unbeknownst to Miller, however, Miel had actually been affiliated with MSF and had shown the letter to Big Boss the moment after receiving it, resulting in his guerrillas joining MSF as well.
Behind the scenes
Miel is a character mentioned in the drama track "Snake & Kaz (Encounter)" included in the radio drama Metal Gear Solid: Peace Walker - Heiwa to Kazuhira no Blues.