On Sept. 21, 2014, Greiner and his Special Forces team were conducting a joint clearing operation in a known insurgent safe haven in the volatile Helmand province, Afghanistan.

The team was ambushed by insurgents within 150 meters of Greiner’s position. A 40-millimeter enemy grenade exploded within five feet of his position, severely injuring Greiner and the team’s interpreter. The team’s medic immediately retrieved Greiner and dragged him into cover and began applying multiple bandages to control his bleeding while requesting an urgent medevac.

The ground force commander attempted to call in emergency close air support procedures to repel the enemy advance, and while doing so, heard Greiner on the radio. Confused, he turned to confirm Greiner’s status. He observed Greiner on the litter receiving medical aid. Greiner had a radio and shrapnel peppered map in one hand, and a fentanyl lollipop in the other. He proceeded to control multiple aircraft to provide CAS for 38 minutes and neutralize the enemy threat, protecting his team and his own medevac helicopter from enemy fire.

For his actions on that day, Greiner was awarded the Bronze Star Medal with Valor.