The border between the two countries is almost 700 miles long. The Chernobyl Exclusion Zone is one of the most important areas of it and lies north of Kyiv. The area was occupied by Russian forces until April 2.
The Chernobyl Exclusion Zone is where Ukrainians fear the Russians will try to come back, possibly in league with Alexander Lukashenko's army.
The commander of a Ukrainian team operating in the zone was the subject of a Yahoo News interview. The soldiers in Andrii's unit have been playing a game of cat-and-mouse with Russian and Belarusian special forces.
There are pockets of intense radiation still present in the zone, despite the fact that the nuclear contamination has died down. The Russian soldiers dug trenches in the red forest. The radioactive samples were taken from the laboratory nearby. A group of Russian soldiers were exposed to dangerous levels of radiation and had to be evacuated to the other side of the world.
According to Andrii, firefights have taken place in the abandoned city of Pripyat, as Russian and Belarusian recon teams attempt to sabotage Ukrainian infrastructure, as well as covertly planting mines. They have been trying to stop them.
It's important for the Ukrainians to maintain a presence as close to the border as possible in order to be able to spot Shahed-136 suicide drones.
The Iranian-supplied drones are small and slow, making them a challenge to detect. An old-fashioned visual detection from a recon team, such as Andrii's, is often the first warning of an incoming swarm of cheap but deadly weapons.
The vast stretch of the Dnipro River just north of Kyiv is one of the only places you can see them before they fly over it.
In February of this year, tens of thousands of Russian troops swarmed into Ukraine in an attempt to encircle the capital and oust the government of President Volodymyr Zelensky. According to Andrii, a false-flag provocation by the Russians or their allies would give Lukashenko the excuse he would need to sell the deployment of troops in Russia's war to his public.
The question of whether or not to become a party to Russia's war has been going on for a long time. Zelensky appealed for an internal monitoring mission to be set up on the border.
According to a senior Western intelligence official, there is no indication that Minsk is going to play a bigger role in the war than it already is. The source said that the Belarusians are training Russian mobiks. It would take a couple of months for Lukashenko to build up enough numbers for an invasion.
Andrii believes that the Russians have learned from their previous failed attempt to seize the city. He said that there are around 10,000 Russian troops in Belarus, as well as Kadyrovtsy, which is loyal to Chechnya's Ramzan Kadyrov.
Several other Ukrainian military sources have told Yahoo News that they fear a push from the north and the east will force the Ukrainians to split their forces. It could affectUkraine's ability to mount more counteroffensives and possibly allow Moscow to regain lost land.
Should the Russians attempt another ground assault toward the Ukrainian capital, Andrii said, they will use massed artillery and large numbers of infantry.
Russia has attempted a similar style of warfare to take the small city of Bakhmut in the east of the country.
There are mud-filled, half-submerged trenches and trees blasted to splinters in the first few scenes of the war.
Satellite images show the Russians are using corpses as barricades, according to one Ukrainian government official who spoke to Yahoo News. The dead human flesh is being used as a defense mechanism.
The creation of a regional grouping of Russian and Belarusian troops was announced by Lukashenko in October. Lukashenko claimed that it was a defensive measure, but he did not mention that he had launched attacks on Ukrainian targets in the past 10 months.
Many Ukrainians think that all of this makes Lukashenko a party to the conflict.
The same human-wave-style attacks that Russia has been using in Bakhmut would be used in such an offensive.
Ukrainian troops have been digging in, preparing fighting positions, planting mines, and constructing tank traps along the border with Belarus. The TDF destroyed bridges and spotted targets for attacks on enemy lines.
The Ukrainains living at the northern border live in relative luxury compared to the Russians. The comforts of home include wood-burning fires, mobile internet, and flat screen TVs. There are makeshift saunas in some of the dugouts along the frontlines in Ukranian.
The Ukrainians have liberated thousands of square miles of territory from Russia after repelling the first attempt to take Kyiv. Concerns about a renewed Russian offensive from the Belarusian direction have lingered for months. Russia has a large pool of poorly trained, but disposable, new recruits as a result of Putin's Mobilization.
The potential attack is at least having a partial effect, whether it is a joint Russian and Belarusian offensive or just another example of Russian military deception. Even if it is only that, the threat at its doorstep cannot be ignored.