Poland (AP) — A rapidly expanding group of U.S. and allied troops and contractors is using phones and tablets to communicate in encrypted chatrooms to provide real-time maintenance advice to Ukrainian troops on the battlefield. As the U.S. and other allies provide more and increasingly complex and high-tech weapons, the maintenance demands are expanding. There were just a bit more than 50 members of what they call the remote maintenance team just a few months ago. That will surge to 150 in the coming weeks, and the number of encrypted chat lines has more than tripled — from about 11 last fall to 38 now.

On the front lines in Ukraine, a soldier was having trouble firing his 155 mm howitzer gun. So, he turned to a team of Americans on the other end of his phone line for help.

“What do I do?” he asked the U.S. military team member, far away at a base in southeastern Poland. “What are my options?”

Using phones and tablets to communicate in encrypted chatrooms, a rapidly growing group of U.S. and allied troops and contractors is providing real-time maintenance advice — usually speaking through interpreters — to Ukrainian troops on the battlefield.

In a quick response, the U.S. team member told the Ukrainian to remove the gun’s breech at the rear of the howitzer and manually prime the firing pin so the gun could fire. He did it and it worked.

The exchange is part of an expanding U.S. military help line aimed at providing repair advice to Ukrainian forces in the heat of battle. As the U.S. and other allies send more and increasingly complex and high-tech weapons to Ukraine, demands are spiking. And since no U.S. or other NATO nations will send troops into the country to provide hands-on assistance — due to worries about being drawn into a direct conflict with Russia — they’ve turned to virtual chatrooms.

The U.S. soldier and other team members and leaders stationed at a base in Poland spoke last week to two reporters who were traveling with Army Gen. Mark Milley, chairman of the Joint Chiefs of Staff, when he visited the facility. Because of the sensitivity of the operation, the troops there spoke on condition of anonymity under guidelines set by the U.S. military. Reporters also agreed not to reveal the name or location of the base or take photos.

Fixing a howitzer, the repair team said, has been a frequent request from Ukrainian troops on the front lines. The need for help with weapons as been growing. Just a few months ago, there were just a bit more than 50 members of what they call the remote maintenance team. That will surge to 150 in the coming weeks, and the number of encrypted chat lines has more than tripled — from about 11 last fall to 38 now.

The team includes about 20 soldiers now, supplemented by civilians and contractors, but the military number may dip a bit, as more civilians come on board. And they expect it will continue to evolve as new sophisticated weapons are delivered to the Ukrainians, and new chatrooms set up to handle them.

“A lot of the times we’ll get calls from right there on the firing line, so there’ll be outgoing or incoming fire at the same time you’re trying to help the forward maintainers troubleshoot the best they can,” said a U.S. soldier who is part of the maintenance team. Sometimes, he said, the chat has to wait a bit until troops can get to a safer location.

A key problem, said one officer, is that Ukrainian troops are pushing the weapons to their limits — firing them at unprecedented rates and using them long after a U.S. service member would turn them in to be repaired or retired.

Holding up his tablet, the U.S. soldier showed photos of the barrel of a howitzer, its interior ridges nearly worn completely away.

“They’re using these systems in ways that we didn’t necessarily anticipate,” said the officer, pointing to the tablet. “We’re actually learning from them by seeing how much abuse these weapon systems can take, and where’s the breaking point.”

The Ukrainian troops are often reluctant to send the weapons back out of the country for repairs. They’d rather do it themselves, and in nearly all cases — U.S. officials estimated 99% of the time — the Ukrainians do the repair and continue on.

Many of the chats are regularly scheduled with depot workers in Ukraine — like the one they call “Coffee Cup Guy,” because his chat has a coffee cup emoji. Other times they involve troops on the battlefield whose gun just blew apart, or whose vehicle stalled.

Sometimes video chats aren’t possible.

“A lot of times if they’re on the front line, they won’t do a video because sometimes (cell service) is a little spotty,” said a U.S. maintainer. “They’ll take pictures and send it to us through the chats and we sit there and diagnose it.”

There were times, he said, when they’ll get a picture of a broken howitzer, and the Ukrainian will say, “This Triple 7 just blew up — what do we do?”

And, in what he said was a remarkable new skill, the Ukrainians can now put the split weapon back together. “They couldn’t do titanium welding before, they can do it now,” said the U.S. soldier, adding that “something that was two days ago blown up is now back in play.”

Doling out advice over the chats means the U.S. experts have to diagnose the problem when something goes wrong, figure out how to fix it, then translate the steps into Ukrainian.

As they look to the future, they are planning to get some commercial, off-the-shelf translation goggles. That way, when they talk to each other they can skip the interpreters and just see the translation as they speak, making conversations easier and faster.

They also are hoping to build their diagnostic capabilities as the weapons systems get more complex, and expand the types and amount of spare parts they keep on hand. For example, they said the Patriot missile system the U.S. is sending to Ukraine will be a challenge, requiring more expertise in diagnosing and repairing problems.

The expanse of weapons and equipment they’re handling and questions they’re fielding were even too complicated for a digital spreadsheet — forcing the team to go low-tech. One wall in their maintenance office is lined with an array of old-fashioned, color-coded Post-it notes, to help them track the weapons and maintenance needs.

The team in Poland is part of an ever expanding logistical network that stretches across Europe. As more nations send their own versions of weapon systems, they are setting up teams to provide repair support in a variety of locations.

The nations and the manufacturing companies quickly put together manuals and technical data that can be translated and sent to the Ukrainians. They then set up stocks of spare parts and get them to locations near Ukraine’s borders, where they can be sent to the battlefield.

Just days before Milley visited the base, Ukrainians traveled to the Poland facility for parts. The visit gave U.S. soldiers a chance to meet someone from their chatrooms face-to-face and swap military patches.

“In the next video chat we had he was wearing our patches in his video,” the U.S. soldier said.

The hub for the growing logistical effort is at Lucius D. Clay Kaserne, the U.S. Army base in Wiesbaden, Germany.

There, in cubicles filling an expansive room, the international coalition coordinates the campaign to locate and identify far-flung equipment, weapons and spare parts in other countries that are needed in Ukraine. They then plan out deliveries — by sea, air and ground routes — to border locations where everything is loaded onto trucks or trains and moved to the war zone.

At least 17 nations have representatives in what’s called the International Donor Coordination Center. And as the amount and types of equipment grow, the center is working to better meld the donations from the U.S. and other nations.

“As we send more additional advanced equipment, like Strykers, like Bradleys, like tanks, of course that sustainment activity will have to increase,” said Douglas Bush, assistant Army secretary for acquisition. “I think the challenge is recognized. I think the Army knows how to do it.”