The Welsh Cavalry has taken part in Exercise Rattlesnake in the United States, one of this year's biggest military exercises.
Fort Polk, the Joint Readiness Training Center (JRTC) in Louisiana, is one of three US Army elite training centres in the world, designed to test troops to their limits.
Much feared, 'The Box' at Fort Polk has been used to train troops, often to breaking point, for decades.
Brigadier General David Doyle, the Commanding General JRTC and Fort Polk, explained the site's extensive history.
"We trained soldiers before World War Two, we trained soldiers before the Vietnam conflict, we trained soldiers before deployments to Afghanistan and Iraq and now we're preparing them for future battlefields," he said.
Forces News was granted exclusive access as British Army personnel, embedded with American soldiers as part of a battlegroup, to take on the 12-day exercise, where it is not only a simulated enemy which is a threat, but the environment of which troops must be aware.
Sergeant 1st Class Michael Angel from Operations Group, JRTC, outlined the challenges: "Poison ivy, poison oak and poison sumac are now coming back out, being as it's the springtime, so try to avoid getting messed up on your hands and rubbing your face.
"Heavy rains and tornadoes. Pigs, we've had a lot of pig encounters, so wild boar.
"There are six extremely poisonous snakes in this area and the cottonmouth likes to chase soldiers."
Warning signs also show alligators present another threat.
To ensure an authentic experience, playing the battlegroup's enemy in Exercise Rattlesnake is a highly trained local force, used to winning in battle, familiar with the terrain, and who call themselves "the most hated unit in the United States Army".
The Welsh Cavalry 1st the Queen's Dragoon Guards have to integrate fast and half of the battlegroup is inserted on Black Hawks.
With many carrying more than 50kg on their backs, once inside 'The Box', it is their first opportunity to see the ground.
The exercise begins with the recce platoon walking through the night on a 15km mission to conduct long-range reconnaissance and surveillance on the enemy and report back vital intelligence.
Lieutenant Edward Carter, A Squadron, 1st The Queen's Dragoon Guards, explained the difficulties of crossing the swamps: "There are lots of unmarked waterways, seasonal waterways as they call them on the maps, most of them aren't marked.
"They often look quite shallow but one of the corporals, unfortunately, crossed in the wrong spot and went head under, at 2am in the morning which wasn't much fun."
Despite the challenges, Brigadier General David Doyle was impressed with their initial performance: "What I watched them do is show just mastery of the fundamentals.
"We had a long-range reconnaissance mission... they walked through some of the worst terrain we have here in Fort Polk.
"They got into a position of relative advantage, they were able to observe the terrain, they were able to render phenomenal accurate reporting about what the enemy was doing and then they passed the Wild Boar, 230 Infantry into the fight.
"It was masterfully done."
The man behind the tests is Colonel Jason Curl, Commander of Operations Group, JRTC.
"It's extremely gruelling," he said.