AMNA NAWAZ: Last week, Ukrainian President Volodymyr Zelenskyy dismissed his tech-savvy defense minister.

That sparked protests among supporters who credit him with helping to transform Ukraine's defense capabilities over the past six months.

Special correspondent Simon Ostrovsky and producer Katia Patin report on the revolutionary technologies and policies that helped drive that transformation.

And a warning: This report includes graphic descriptions of war.

SIMON OSTROVSKY: Victory gardens, war bonds, ration books, every war has its home front.

In Ukraine, a secret group of volunteers, including this woman who goes by the call sign Little Witch, are supporting their troops by making weapons using 3-D printers.

Like so many others in this country, she's transformed her small apartment into a high-tech printing armory.

"LITTLE WITCH," Volunteer Weapon Maker (through translator): It's hot as hell in here.

SIMON OSTROVSKY: An I.T.

specialist in Kyiv, Little Witch is one of more than 3,500 civilians volunteering for an organization called Drukarmija, Ukrainian for Print Army.

Their network of at-home 3-D printers is revolutionizing modern warfare.

People like her are able to connect directly to soldiers on the front line through an online marketplace where troops can browse products, place orders, and even leave reviews.

Everything is free, funded entirely through voluntary donations.

"LITTLE WITCH": Our guys sent me a video with what we printed at home and said, like, yesterday you sent it to us, and today your items killed Russian guys.

They said, like, perfect quality.

SIMON OSTROVSKY: She told us each printer costs around $1,000 and uses spools of plastic thread to make gear like gun magazines, casings for explosives or bodies for handheld drone detectors.

So this is the casing that they produce here right at home, and, obviously, this doesn't have all of the insides that it needs to fly, but it's a critical part of the interceptor drone.

Drones like these are used to shoot down Shaheds that Russia fires at Ukraine routinely.

So what made you get involved with this in the first place?

"LITTLE WITCH": Help our guys to survive.

We want Ukraine to be free, and we want that Russia leave us alone forever.

SIMON OSTROVSKY: Four years into a war against a country with an economy 10 times its size, Ukraine is fighting back with ingenuity, instead of scale.

On another platform called Brave1 Market, soldiers earn points for confirmed kills and can redeem them for weapons, a gamification of war designed to keep them motivated.

Andrii is one of the employees at Brave1, whose job it is to verify kills in order to correctly award those points.

Do you find that it is an effective motivation tool?

Why are soldiers so interested in collecting these points?

ANDRII, Brave1: First of all, you have some kind of cash back.

You have used two drones on a Russians, you have killed them.

Then you have got your two drones back from the marketplace.

Then you will use it again and again and again and again.

SIMON OSTROVSKY: Andrii told us he's able to confirm the accuracy and point value of every kill because, on the war's tech-dominated front line, nearly every mission is now recorded by drone or by a soldier's head-cam.

He says he watches hundreds of mission videos every day.

What's the most difficult video you have ever had to review?

ANDRII: Oh, yes, I remember this guy's face.

They hit him with Mark 19 grenade.

He was wounded.

Then the second one tear him open.

His belly, his guts went out, and then the third hit was with the M-67 grenade.

It just landed in his guts, like in the stomach.

And you can imagine the results.

SIMON OSTROVSKY: Remarkably, Brave1 and the Print Army's products both get delivered directly to soldiers on the front line, reaching positions at Amazon Prime speed.

"News Hour" followed one of the deliveries from the Print Army to a soldier serving in an undisclosed location in Ukraine.

ZHABA, Ukrainian Soldier (through translator): To make this work when it's dropped from a drone, we used an inertial firing pin.

SIMON OSTROVSKY: This Ukrainian soldier showed us how 3-D printed items are also used to adapt conventional weapons for modern drone warfare.

A lot of these items look like toys, but they're actually very dangerous weapons.

They say necessity is the mother of invention.

And during this war with Russia, Ukraine has been incredibly inventive.

The Army of volunteer 3-D printers is just one of the ways that Ukraine has adapted to fight a much larger enemy.

The Print Army says its volunteers shipped more than 527 tons of printed products like this last year alone.

Yuliia Myrna was preparing to enlist in the Ukrainian army before she joined the government-backed Brave1 platform, dedicating her digital marketing experience to reinventing the supply chain of war.

Is it fair to characterize the Brave1 marketplace as something like an Amazon for war?

YULIIA MYRNA, Brave1: It's much more than, I think, Amazon, because we not only offer them a big catalog.

If we speak about our companies, so we help them to see how effective their product on the front line and how they can improve it.

SIMON OSTROVSKY: While the Print Army brings manufacturing into the home, Brave1 brings the battlefield to the manufacturer.

Products purchased on Brave1 are tracked and analyzed, generating data gold for weapons makers, who are able to see which weapons are making the biggest difference in the war.

Brave1 isn't just a marketplace or an Amazon for soldiers to get the equipment that they want.

It's also a venture capital space, where technologies are put forward, and the promising ones attract funding from the government and private investors.

And it's thanks to the platform that many of the weapons in this room got developed in the first place.

Brave1 is reimagining the entire model for military procurement, offering each type of user a different service wherever they are on the battlefield.

And they're doing that by incentivizing soldiers to be as effective and lethal as they can possibly be, doling out the maximum points for eliminating targets that the Ukrainian government has identified as its top priorities.

Some of the highest point values are awarded for taking out a plane or helicopter, evacuating wounded soldiers, and destroying enemy air defense systems.

Capturing a Russian soldier is worth ten times the value of killing one.

While Andrii works from a desk in Kiev, the hundreds of videos he's verifying offer an up-close and gruesome view of life and death on the front line.

How does it feel?

I mean, how do you feel after having watched so many kill videos yourself?

ANDRII: Well, that's war.

We are fighting our own small war.

I have a sense of duty.

And I also want my father to get back home safe.

SIMON OSTROVSKY: Your father fights on the front lines?

Is it a tough job?

ANDRII: In a way, it is.

SIMON OSTROVSKY: What's tough about it?

ANDRII: The gruesomeness of this.

It's kind of like, if you watch one video, that's OK.

Two, three, four, OK.

But several hundred a month like this, yes, it kind of it... SIMON OSTROVSKY: It affects you psychologically?

ANDRII: Yes.

SIMON OSTROVSKY: Last week's removal of the chief architect of Ukraine's digital wartime transformation, Defense Minister Mykhailo Fedorov, is the biggest military leadership shakeup in the country since Russia invaded, leaving Ukrainians wondering whether his military reforms are here to stay.

For the "PBS News Hour," I'm Simon Ostrovsky in Kyiv.