Shyrokyne, Ukraine (CNN) On the front lines of Ukraine's war with Russia, the conditions are basic and the enemy is close. At a Ukrainian position in the southeast of the country, the troops fight from dirt trenches that twist and turn through the flat terrain.

One soldier with a thick mustache stands at a lookout, his machine gun nestled in his shoulder. Just six hundred yards away, the sandbags of the Russian-backed separatists can be seen.

"They use drones to drop mines on our positions," the commander, Pavel Sergeevich, tells CNN, nodding in the direction of the enemy.

He says one of his men was shot dead by a sniper 10 days ago. There's supposed to be a ceasefire, but it is broken regularly.

After five years and about 13,000 deaths, many in the outside world had forgotten the conflict in Ukraine until America's political crisis catapulted it into the headlines again

In July, when President Donald Trump was encouraging new Ukrainian President Volodymyr Zelensky to investigate his political rival, former Vice President Joe Biden, nearly $400 million in military and security aid to Ukraine had already been suspended and would continue to be for months. Whether the aid was held up to pressure the opening of a corruption inquiry and whether that is impeachable is now a key part of the action House Democrats are launching against the President.

By the time Sergeevich and his men learned about the freeze, that aid had already been released. But the delay left a chill.

Sergeevich told CNN he was "unhappy and disappointed. America is our strongest and most important ally."

How the US is involved

It's hard to find much evidence of American military aid on the front lines beyond US-issued tourniquets and bandages and night vision goggles. This battlefield near Shyrokyne, with its trenches hand-dug with shovels, seems to have more in common with stories of World War I than 21st century conflicts.

The key weapon the United States has agreed to sell is the Javelin, an anti-tank missile, that was mentioned by Zelensky in his July 25 call with Trump . The United States has decreed that the system may not be used on the front lines, where it might lead to an escalation of force on the Russian side.

A schoolroom in Shyrokyne, a village abandoned by its residents after it was hit by artillery at the start of the war.

But dozens of conversations with Ukrainian soldiers and civilians have revealed how the people feel themselves locked in a David and Goliath fight with Russia. Having the backing of the United States is seen as critical to leveling the playing field a little as Ukraine tries to win back parts of the country now run by Russian-backed separatists.

At the other end of Ukraine, about as far away from Sergeevich's trenches as you can get, there are clearer signs of US support. Military mentors from the United States join instructors from Canada, the United Kingdom and several other NATO allies to train Ukrainian forces at the Yavoriv Combat Training Center.

On the day of CNN's visit, Ukrainian soldiers practiced a mounted assault under the watchful eye of US Army Capt. Matthew Chapman.

"I feel very proud of the work we've done, the work we've put into our training exercises," Chapman says. "We can see the Ukrainian soldiers, we can see them improve and we can see them become closer as a team and a lethal fighting force."

Ukrainian soldiers are trained by Americans in the west of the country.

When asked about his reaction to the temporary freezing of US aid, Chapman said, "personally, I don't pay attention to US ... foreign policy or politics while I'm here. We are solely focused on the mission at hand ... It has not even come up in conversation."

His Ukrainian counterpart, Lt. Nazar Shpak, agrees. Asked whether the United States is a reliable ally, he nods emphatically "completely, yes, completely."

Concern about Putin, and about Trump

Back in the east, the real impact of this conflict is still unfolding. Nearly 1.5 million people have been displaced as town after town has been smashed by heavy bombardment.

In the mining town of Toretsk, half of the population has left and most of the coal mines are shut. In the central square, the burned-out town hall stands empty, a grim reminder of the bitter battle between separatists who captured the town and the Ukrainian army who forced them out again.

History teacher Leonid Makarov says it worries him that President Trump seems to court Russian President Putin.

The nearest front line is now more than five miles away, but Leonid Makarov says the fighting is far from over. The 26-year-old history teacher lost one of his students last year. Daria Kazemirova was killed just days after her 15th birthday when an artillery shell fired by Russian-backed separatists landed in her grandmother's garden, he says.

Makarov still struggles to make sense of it and of President Trump's seemingly mercurial attitude towards Ukraine and Russia.

"When I hear President Trump say Vladimir Putin is a nice guy -- it's just weird. It concerns me. Putin killed my student."

Yelena Salaeva has not been home in five years, after she was hit by shrapnel picking tomatoes in her garden.

At a nearby center for elderly people, Yelena Salaeva says she no longer cares who wins the war. The pensioner was forced to leave her home five years ago after being wounded by shrapnel while picking tomatoes in her garden. She has not been able to go back.

"We just want there to be no more war and for everyone to have their own peaceful life."

Fears for the future

Last month, Zelensky announced his support for a phased peace plan, in which the occupied areas of eastern Ukraine would get special self-governing status after holding local elections.

But it is a long road ahead and the political crisis in the United States could yet impact Ukraine again. There is a lingering fear that bipartisan support for Ukraine could be poisoned by increasing polarization brought by the impeachment process. And if legislators will no longer stand and speak up together, that could strengthen Russia's hand.

Back in his trench, Pavel Sergeevich shrugs and says his men will keep fighting, with or without US support.

"We will fight even if the whole world is against us. This is our land. What choice do we have?"