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Mark Hayward was tapped to teach the Ukrainian Territorial Defense how to use the new British anti-tank weapons, but there was only one small problem: He had no idea how to use the devices himself, and he had just half a day to bring Ukraine's forces up to speed. 

"I used a variety of anti-armor weapons, but dumb ones were state of the art when I got out of the service," Hayward told Fox News Digital. "I had no experience with the Javelin whatsoever." 

Hayward, former Special Forces soldier, left the army in 2007 but traveled to Ukraine in 2022 to join up with the Foreign Legion there and assist the war effort when his friend suggested that he might be the right guy to teach the Ukrainian territorial defense how to use the Next Generation Anti-tank Weapon (NLAW). 

"I went to stop the Russians from shelling Ukrainian cities by whatever means necessary," Hayward told Fox News Digital, admitting that he hadn’t expected Ukraine to "last two weeks" or that he would "come back." 

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Hayward stepped up to teach the soldiers how to use the NLAWs, and said he had just "12 hours" to figure out how to use the device himself. He was able to contact friends in the U.S. who helped him track down the user manuals, which he studied overnight before teaching the class. 

"We said we're probably not the right guys, but they said ‘you’re all we have,’ so we read the manuals, we looked at everything we could get our hands on," Hayward explained. "We were self-taught Javelin instructors, and we were super lucky because after a couple of days, other volunteers in the U.S. and U.K. would come out of the woodwork … so we had other volunteers come forward." 

The trickiest part – after learning on the fly how to use the weapon – was teaching the troops without much ability to actually try out the weapon before deploying them into the field, due to limited supplies. Each Javelin had a non-rechargeable battery that was good for only two things: once the Command Launch Unit (CLU) was on, the battery could either power top-notch thermal night sight for four hours or try to launch between two and four missiles.

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"It's kind of variable depending on how much time you spend acquiring your target," Hayward said. "The Marines had not been issued enough batteries to do anything other than get out there and shoot some missiles, which meant that, since they didn't have any other choice, the guns were almost like a Hail Mary for them."

The Ukrainian engineers provided some relief by helping build prototype external rechargeable battery packs – a field innovation they managed to pull together within 48 hours. But without anyone to help them verify the safety, they had to deploy the batteries without much testing. 

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They plugged the prototype into a $100,000 CLU, and it worked without a problem. 

"It didn’t blow up and it worked just fine, and suddenly we were in business," Hayward said. "Suddenly, we were in business, we could actually train on how to use these missiles." 

Sending the troops out with minimal practical training unnerved Hayward, and he can only hope that the U.S. continues to provide the kind of weapons and training the Ukrainians need to defend their homeland. 

"I stayed up a lot of nights," Hayward confessed. "I've spent a lot of prayers. I've spent a lot of tears. We are not giving these guys everything we can."

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"It would be so easy to give them what they need if we could just get through the bureaucracy and get it done," he added. "That was the most difficult thing I have encountered and I am still encountering it."