Two muffled booms broke the crisp, high desert air of Piñon Canyon, sending troops in every direction ducking to the cactus-strewn dirt.
"Incoming," yelled Col. Scott Gallaway, the unit's commander, heralding the opening salvos of the largest exercise ever held by Fort Carson's 4th Combat Aviation Brigade at the Piñon Canyon Maneuver Site.
Within 12 minutes, the first AH-64 Apache helicopters took off. And Gallaway, a veteran Apache pilot with five overseas tours, made for a cockpit to help ferret out the enemy.
The exercise that began last week, called "Eagle Strike," marked the culmination of a year of training, resulting in a well-coordinated dance across the piñon tree dotted landscape of southeast Colorado.
In the past, individual battalions of hundreds of troops from the aviation brigade trained at the 235,000-acre site northeast of Trinidad. This time, nearly 2,000 of the brigade's 2,800 troops will live and train there, no matter the weather, through early March.
"This is to prepare us for any worldwide contingency situation," said Maj. Talon Young, a 4th Infantry Division future operations officer.
Two other Fort Carson units - the 1st and 2nd brigade combat teams - are deploying to Afghanistan this year.
Gallaway said the current exercise ensures the brigade can go anywhere in the world.
"I'm sure we will deploy sometime in the future," Gallaway said. "Where and when, I don't know exactly."
For now, they're employing a brand of training called "decisive action" - a regimen predating the brigade's formation in 2013 that aims to prepare soldiers for more traditional, large-scale and tank-on-tank warfare that epitomized the nation's cold-war military style. It's a stark contrast to the counterinsurgency tactics that became the staple of the wars in Iraq and Afghanistan.
For the 4th Combat Aviation Brigade, that means giving Apache pilots a chance to hone their tree-buzzing skills, Gallaway said.
Known as "tank killers," the attack helicopters carry Hellfire missiles that leave tanks looking like pumpkins hit with dynamite.
One exercise calls for several Apaches to provide cover fire and destroy enemy artillery crews while eight-wheeled Stryker vehicles from Fort Carson's 1st Brigade Combat Team fall back from their reconnaissance outpost.
Pilots must fly fast and stay low, blending into the piñon trees and popping out from behind hillsides just long enough to launch missiles.
Some helicopters will take part in live-fire training at Fort Carson, while helicopters at Piñon Canyon will practice their maneuvers without launching missiles.
Often, they hover and zip no higher than 50 feet from the ground.
"We need to get back to the basics ... of what an attack battalion was built for," said Lt. Col. Timothy Jaeger, commander of the brigade's 4th Attack Reconnaissance Battalion of the 4th Aviation Regiment.
With nearly the entire brigade taking part, new challenges abound. Soldiers in Piñon Canyon plan to remotely maneuver the brigade's new Gray Eagle drones - unmanned planes with 56-foot wingspans - above Fort Carson to the northwest.
Units must create their own pop-up command centers on grassy hillsides 100 miles from Fort Carson - complete with meal trucks, a helicopter maintenance area and satellite hookups to send and receive classified information.
"This is like being in a new country, setting up all new operations, and then helping with deep attacks," Gallaway said.
They began packing for the exercise Feb. 12, and arrived at Piñon Canyon on Tuesday, after being delayed by a snowstorm.
Whether this specific training translates to the real world remains unclear. The war in Afghanistan continues to drag on as the nation's longest-running war on record. The aviation brigade spent most of 2016 in the war zone. And a couple companies continued the fight last year - the most recent having returned late last year.
If they do get sent there, the units will be ready, Jaeger said.
The vast majority of the troops only know the counterinsurgency tactics employed in Afghanistan and Iraq. It's a slower-paced fight than the "decisive action" style of fighting - one largely spent 1,000 to 2,000 feet above the ground, where pilots have more time to react to incoming fire.
For now, they need to be ready for anything.
"It's just a different way than we've been fighting for the last 10 to 15 years," Gallaway said.