CINCU, Romania — A massive, multinational, combined-arms, live-fire exercise lit up the Romanian countryside in a show of force July 18, carrying out a NATO goal to demonstrate joint strength to deter Russian aggression.

By the end of nearly an hour, the hillsides smoked from the unleashing of artillery, mortars, rockets and fire from tanks and combat vehicles as well as helicopters and fighter jets from Romania, the United States, Croatia, Armenia, Montenegro — the newest NATO member — and Ukraine.

Last year at the NATO summit in Warsaw, Poland, the 28 nations decided it was time to shift from a military posture that reassured allies and partners in Eastern Europe to full-on deterrence as Russia’s behavior in the region continues to cause concern.

Exercises like CALFEX — part of Saber Guardian 2017 taking place across seven countries in Europe — are designed to show the world what the U.S. and its NATO partners and allies are capable of doing should an attack by a near-peer adversary occur. The U.S.-led Saber Guardian is the largest exercise in the Black Sea region this year, and it consists of more than 25,000 service members from more than 20 allied and partner nations.

"Deterrence is about capability, it’s about making sure that any potential adversary knows that we are prepared to do whatever is necessary," U.S. Army Europe commander Lt. Gen. Ben Hodges said during a news briefing following the exercise.

"What escalates tensions is when we look weak, not connected, not prepared, that is what invites aggression," Hodges said. "If we stay strong together … then I think the possibility of any mistake is much, much lower. For 40 years in the Cold War, we had huge militaries facing each other and 40 years of peace."

Three years ago the U.S. Army pulled its last tanks out of Europe, but with the Russian invasion of Crimea in Ukraine, the U.S. has been rapidly building its presence back up in order to deter Russia from carrying out anything similar in other neighboring countries.

At CALFEX at the Romanian Joint National Training Center, heavy combat vehicles and powerful artillery weapons lined the hillsides and demonstrated that the U.S. and its allies can operate together in challenging terrain and complex missions.

First Lt. Joshua Arnold, the platoon commander of a Paladin battery, told Defense News the day before the big event on the hillside overlooking the terrain planned for the exercise that he saw this as a chance to show the world what the U.S. Army and its allies have through an enormous display of fire power.

A total of 18 Paladin M109A6 howitzers lined the hillside together with Romanian 125mm guns as preparation for the big day.

The exercise was based on a fictional scenario where European countries are attacked by a near-peer adversary with the same capabilities as NATO nations "with the intention to gain control over the economic activities of the Black Sea region countries," according to the exercise’s script.

Action began with forces in tactical assembly areas as intelligence, surveillance and reconnaissance assets as well as artillery radar searched for the enemy. Intelligence officers were able to pinpoint two enemy mechanized infantry battalions that had invaded territory under surveillance.

Intelligence forces identified enemy air defense units. Joint U.S. and Romanian artillery units, led by the 1st Cavalry Division Artillery from Fort Hood, Texas, coordinated the suppression of the enemy's assets using fires from U.S. Multiple Launch Rocket Systems, or MLRS, U.S. High Mobility Artillery Rocket Systems, or HIMARS, as well as Romanian versions of the same, that provided a window for friendly maneuver forces to advance.

Infantry quickly moved from the top of a ridge, downhill, taking position midway overlooking enemy forces on the next hillside and were quickly surrounded in smoke obscurant as a Romanian mortars team fired on the enemy to allow the infantry to advance.

As firing continued from HIMARS and MLRS assets, MiG-21 LanceR jets dropped 100-kilogram bombs over the heads of the enemy. The jets came from Romania's 71st Air Base in Campia Turzii.

While the jets made passes, Romanian Puma helicopters flew in and fired at the enemy while a U.S. infantry company with Bradley Fighting Vehicles, consisting of Montenegrin partners, as well as a Croatian infantry company, established strong points on the battlefield. Then AH-64 Apache attack helicopters joined in and replaced the Puma mission, firing from 30mm cannons and shooting rockets to destroy enemy combat vehicles.

A multinational armor company under Romanian command with one Romanian and one U.S. armor platoon — with U.S. M1 Abrams tanks and upgraded Romanian T-85 tanks — rolled in and continued to pressure enemy forces with a barrage of firepower. It was joined by a Ukrainian air assault company and a Romanian air defense artillery company with Gephard short-range air defense systems to continue to suppress enemy forces.

The enemy then brought in its reserve forces reported to be advancing toward defensive lines. The multinational task force Iron Guardian conducted a simultaneous fire attack on the enemy reserves "in order to hit the enemy all at once and cause shock and surprise," according to the script read allowed during the exercise.

A "torrential volley of destruction" rained down on the enemy, the CALFEX announcer said over loudspeakers, resulting in "utter defeat."

Jen Judson is an award-winning journalist covering land warfare for Defense News. She has also worked for Politico and Inside Defense. She holds a Master of Science degree in journalism from Boston University and a Bachelor of Arts degree from Kenyon College.

More In Training & Sim