8 photos of Marines training during a gas attack that look eerily like World War I

Few things in battle are scarier than a gas attack during a ground assault. The air grows thick with toxic mist, and the world shrinks to the view from a hot, sterile mask.

It’s the attack most troops have dreaded since the tactic was first used on a large scale at the Second Battle of Ypres over 100 years ago. Chemical warfare was outlawed in the wake of World War I, but it’s something that American forces still prepare for.

During a recent mock battle with the Australia military dubbed Exercise Koolendong in Darwin, Australia, Leathernecks from the 1st Battalion, 1st Marine Regiment trainers dropped CS gas into fighting positions to force the troops to deal with a chemical attack in the middle of a firefight.

Photos from the exercise show how difficult it is for troops to fight during a chemical attack and provide an eery reminder of the mustard gas-blanketed battlefields on the War to End All Wars.

1. The assault began with simulated artillery firing in on Marine and allied positions

Marines with 1st Battalion, 1st Marine Regiment, watch illumination from artillery fall to the ground during a live fire range August 18, 2016, at Bradshaw Field Training Area, Northern Territory, Australia. The range was the final training evolution of Exercise Koolendong 16, a trilateral exercise between the U.S. Marine Corps, Australian Defence Force and French Armed Forces New Caledonia. Marines held a defensive position while engaging targets and working through the CS gas, which simulated a chemical attack. (U.S. Marine Corps photo by Sgt. Sarah Anderson)

Marines with 1st Battalion, 1st Marine Regiment, watch illumination from artillery fall to the ground during a live fire range August 18, 2016, at Bradshaw Field Training Area, Northern Territory, Australia. The range was the final training evolution of Exercise Koolendong 16, a trilateral exercise between the U.S. Marine Corps, Australian Defence Force and French Armed Forces New Caledonia. Marines held a defensive position while engaging targets and working through the CS gas, which simulated a chemical attack. (U.S. Marine Corps photo by Sgt. Sarah Anderson)

2. Despite the gas drifting into their positions, the Marines had to stand their ground

Marines with Company C, 1st Battalion, 1st Marine Regiment, fire down range during a CS gas attack during a live fire range August 18, 2016, at Bradshaw Field Training Area, Northern Territory, Australia. The range was the final training evolution of Exercise Koolendong 16, a trilateral exercise between the U.S. Marine Corps, Australian Defence Force and French Armed Forces New Caledonia. Marines held a defensive position while engaging targets and working through the CS gas, which simulated a chemical attack. (U.S. Marine Corps photo by Sgt. Sarah Anderson)

Marines with Company C, 1st Battalion, 1st Marine Regiment, fire down range during a CS gas attack during a live fire range August 18, 2016, at Bradshaw Field Training Area, Northern Territory, Australia. The range was the final training evolution of Exercise Koolendong 16, a trilateral exercise between the U.S. Marine Corps, Australian Defence Force and French Armed Forces New Caledonia. Marines held a defensive position while engaging targets and working through the CS gas, which simulated a chemical attack. (U.S. Marine Corps photo by Sgt. Sarah Anderson)

3. Range safety officers peer through the gas-filled haze to keep Marines injury free

Range safety officers observe Marines from 1st Battalion, 1st Marine Regiment hold a defensive position while surrounded by CS gas August 18, 2016, at Bradshaw Field Training Area, Northern Territory, Australia. The range was the final training evolution of Exercise Koolendong 16, a trilateral exercise between the U.S. Marine Corps, Australian Defence Force and French Armed Forces New Caledonia. Marines held a defensive position while engaging targets and working through the CS gas, which simulated a chemical attack. (U.S. Marine Corps photo by Sgt. Sarah Anderson)

Range safety officers observe Marines from 1st Battalion, 1st Marine Regiment hold a defensive position while surrounded by CS gas August 18, 2016, at Bradshaw Field Training Area, Northern Territory, Australia. (U.S. Marine Corps photo by Sgt. Sarah Anderson)

4. Getting a gas mask on in time to stay alive in the middle of a fight can be a daunting task

Maj. Christopher W. Simpson, commanding officer, Company C with 1st Battalion, 1st Marine Regiment, dons a mask while surrounded by CS gas during a live fire range August 18, 2016 at Bradshaw Field Training Area, Northern Territory, Australia. The range was the final training evolution of Exercise Koolendong 16, a trilateral exercise between the U.S. Marine Corps, Australian Defence Force and French Armed Forces New Caledonia. Marines held a defensive position while engaging targets and working through the CS gas, which simulated a chemical attack. (U.S. Marine Corps photo by Sgt. Sarah Anderson)

Maj. Christopher W. Simpson, commanding officer, Company C with 1st Battalion, 1st Marine Regiment, dons a mask while surrounded by CS gas during a live fire range August 18, 2016 at Bradshaw Field Training Area, Northern Territory, Australia. (U.S. Marine Corps photo by Sgt. Sarah Anderson)

5. Despite the restricted vision and discomfort, Marines still have to put rounds down range and keep the enemy at bay

Marines with Company C, 1st Battalion, 1st Marine Regiment, fire down range during a CS gas attack during a live fire range August 18, 2016, at Bradshaw Field Training Area, Northern Territory, Australia. The range was the final training evolution of Exercise Koolendong 16, a trilateral exercise between the U.S. Marine Corps, Australian Defence Force and French Armed Forces New Caledonia. Marines held a defensive position while engaging targets and working through the CS gas, which simulated a chemical attack. (U.S. Marine Corps photo by Sgt. Sarah Anderson)

Marines with Company C, 1st Battalion, 1st Marine Regiment, fire at enemy positions during a CS gas attack during a live fire range August 18, 2016, at Bradshaw Field Training Area, Northern Territory, Australia. (U.S. Marine Corps photo by Sgt. Sarah Anderson)

6. Troops take precious minutes testing the air to determine how best to survive the attack

A Marine with Company C , 1st Battalion, 1st Marine Regiment, tests the air for safety after a gas attack August 18, 2016, at Bradshaw Field Training Area, Northern Territory, Australia. The range was the final training evolution of Exercise Koolendong 16, a trilateral exercise between the U.S. Marine Corps, Australian Defence Force and French Armed Forces New Caledonia. Marines held a defensive position while engaging targets and working through the CS gas, which simulated a chemical attack. (U.S. Marine Corps photo by Sgt. Sarah Anderson)

A Marine with Company C , 1st Battalion, 1st Marine Regiment, tests the air for safety after a gas attack August 18, 2016, at Bradshaw Field Training Area, Northern Territory, Australia. (U.S. Marine Corps photo by Sgt. Sarah Anderson)

7. It’s just as important for medical personnel to practice treating and evacuating casualties during a chem-bio attack

Marines and sailors with 1st Battalion, 1st Marine Regiment, evacuate a simulated casualty during a live fire range August 18, 2016, at Bradshaw Field Training Area, Northern Territory, Australia. The range was the final training evolution of Exercise Koolendong 16, a trilateral exercise between the U.S. Marine Corps, Australian Defence Force and French Armed Forces New Caledonia. Marines held a defensive position while engaging targets and working through the CS gas, which simulated a chemical attack. (U.S. Marine Corps photo by Sgt. Sarah Anderson)

Marines and sailors with 1st Battalion, 1st Marine Regiment, evacuate a simulated casualty during a live fire range August 18, 2016, at Bradshaw Field Training Area, Northern Territory, Australia. (U.S. Marine Corps photo by Sgt. Sarah Anderson)

8. As America’s potential adversaries look for ways to defeat U.S. troops with unconventional weapons, it’s important that the services practice fighting during a chemical or biological attack — no matter how remote the possibility

Marines with Company C, 1st Battalion, 1st Marine Regiment pack up their gear after completing the final live fire range of Exercise Koolendong 16 at Bradshaw Field Training Area, Northern Territory, Australia on August 18, 2016. The range was the final training evolution of Exercise Koolendong 16, a trilateral exercise between the U.S. Marine Corps, Australian Defence Force and French Armed Forces New Caledonia. Marines held a defensive position while engaging targets and working through the CS gas, which simulated a chemical attack. (U.S. Marine Corps photo by Sgt. Sarah Anderson)

Marines with Company C, 1st Battalion, 1st Marine Regiment pack up their gear after completing the final live fire range of Exercise Koolendong 16 at Bradshaw Field Training Area, Northern Territory, Australia on August 18, 2016. The range was the final training evolution of Exercise Koolendong 16, a trilateral exercise between the U.S. Marine Corps, Australian Defence Force and French Armed Forces New Caledonia. Marines held a defensive position while engaging targets and working through the CS gas, which simulated a chemical attack. (U.S. Marine Corps photo by Sgt. Sarah Anderson)

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