It is a 90-kilometre drive from the Belarus border straight down to the Ukrainian capital of Kiev. At a push, a Russian armoured force could get there in about two days.
The latest intelligence shows Russia’s crack combat battalions in Belarus moving towards Ukraine’s border, ostensibly to begin an exercise on Thursday.
Their presence in the former Soviet Union state numbers about 30, and they could lead any assault that President Vladimir Putin is contemplating.
A year ago, Belarus President Alexander Lukashenko would not have been as open to a rapid increase in Russian troops on his soil, but now his country is becoming a platform that Moscow can populate not only with formations but missiles capable of nuclear strikes.
That is why, whatever happens in Ukraine over the coming weeks, Nato is rapidly reinforcing what it calls its eastern flank, a move unlikely to be reversed any time soon.
Three decades after the Cold War ended with the peace dividend leading to smaller armies, western powers are rapidly revising their war philosophy to include a growing focus on tanks and artillery.
In the meantime, Nato reinforcements from America, Britain, Germany and France are heading to the eastern flank of the Baltic states, Poland and Romania to shore up their defences and send a message of deterrence to Mr Putin. The Russian build-up in Belarus also now threatens the southern flank of the Baltics and Poland.
If Mr Putin attacks Ukraine, Nato forces with be in very close proximity. That may well be part of his calculation. Nato might arrive but will not readily intervene in a country outside the alliance.
The current movements by Moscow’s forces suggest that the Kremlin is preparing for a swift strike before the combined Nato and Ukraine forces strengthen any further.
“It is likely that the Russian forces would never have as favourable situation as they do right now,” said Sam Cranny-Evans, a military analyst at the Rusi think tank in London.
“There are considerable signs that their forces have moved through readiness levels quite deliberately.”
In the past decade, the Russian armed forces have improved considerably, with tactics honed from the wars in Syria, Ukraine and latterly Chechnya.
The Russian military has been very thorough in its preparation for war. Since last year, it has moved heavy armour and artillery from across the country into massive “tank parks” close to the Ukraine border. They are now ready to be united with troops numbering 100,000.
Russian units are broken into three categories. One is well-trained regular soldiers, two a combination of regulars, reservists and conscripts; and three mainly conscripts who, under contract, cannot deploy outside Russia.
It is the level-one troops who are now in their armoured vehicles, moving out of the tank parks in readiness for long-planned exercises.
Those manoeuvres may well turn into operations at Mr Putin’s direction. That order will be signalled by a barrage of Ukraine’s critical government and military installations, mostly by the Iskander-M launchers. There are 52 Iskanders positioned around Ukraine, each with a range of 500km carrying a 700-kilogram warhead that could devastate a state building, telecommunications site, bridge or military headquarters.
Missile-capable warships in the Black Sea and Caspian Sea will also fire their weapons, which include cruise missiles with a 1,500km range.
Simultaneously, a mass electronic warfare operation, including cyber attacks, will take down Ukraine’s communications and its air defences. This would open the way for Russia’s air force to strike more targets.
Once the country’s key military infrastructure is neutralised – something that could happen very quickly – the armoured thrust will commence. This could come from three directions – Belarus in the north, to the west direct from Russia and along the southern Sea of Azov route, linking with Crimea.
Russia’s highly capable T90 main battle tanks along with armoured personnel carriers will spearhead the ground attacks. They will adopt the Russian tactic of halting whenever they hit a strongpoint, waiting for the heavy artillery to roll up, with their firepower mostly directed by drones.
“The Russian way really places artillery at the top of the chain. It is their God of War,” Mr Cranny-Evans said.
“The key goal is to really create a lot of attrition against the enemy force without the tanks actually having to get involved. They seek to pull the enemy’s forces into what they call a fire trap, essentially pinned down by the Russian armour, allowing the artillery to finish the job.”
Despite the late addition of advanced anti-tank weapons sent from US and UK, along with its own tanks, air force and anti-aircraft systems, Ukraine is likely to be overwhelmed.
But it will certainly be able to inflict losses, perhaps enough to cause the country’s Russian population to question the invasion. There are also 80,000 Ukraine reserves who have been trained by regular officers every weekend since 2015 with a view to an insurgent tactic of “having a shooter at every window”.
The Russians will be looking for a rapid military conquest that would lead to a political settlement.
The coming weeks are also the prime moment to attack before the great “Rasputitsa” thaw comes in early March turning the ground into a quagmire, difficult but not unsurpassable for tanks.
The crack troops being moved into position can only remain at a high readiness for combat for a month before they will be rotated out, sometime in March.
If that does happen, what would Mr Putin have achieved?
The West would have certainly learnt that after two decades of counter-insurgency in Iraq and Afghanistan, it must revert to conventional warfare and the prospect of state-on-state conflict.
Mr Putin may well have already achieved his aims. His forces – potentially nuclear equipped – are now firmly in Belarus, a land-grab made without loss of life. Nato is now highly unlikely to discuss Ukraine’s membership. The West will also gladly allow the Nord Stream 2 gas pipeline from Russia to Germany to be switched on if it averts war, despite substantially filling Moscow’s banks, allowing for military growth.
Mr Putin’s new-found friendship with China’s President Xi Jinping could have another dimension. If the West is tied up in Europe, its attention is drawn away from the “Indo-Pacific tilt” that had been pushed by Britain and others.
“Even if the crisis was to go away today, certain things have already changed,” said Dr Neil Melvin, Rusi’s director of international security studies.
“There is going to be the reshaping of the European security situation around the Russian threat. What we also see as a result of the Ukraine crisis is this growing inter-linkage across the Eurasian landmass between European and Indo-Pacific security.”
War or no war, the strategic outlook in Europe has undergone is biggest transformation in four decades.