When Ukrainian forces crossed the Russian border in the early hours of Aug 6, they sliced through Moscow’s defences like a knife through butter.

Strict operational security obviously helped. Ukrainian commanders only learnt of the operation three days in advance; ordinary troops only on the day it took place.

But the Ukranianians were also pushing on a Russian weak spot, where a shortage of decent manpower was exacerbated by the absence of a clear Russian chain of command.

It is in stark contrast to last year’s failed counter-offensive.

“Just imagine the amount of chaos we could bring there,” said one veteran of that operation in Zaporizhzhya.

“I wish I was there – and all my mates, still serving or decommissioned, too.”

In the initial chaos of the thrust, Moscow’s military response was hampered by a lack of clarity on who was in charge.

“This AFU (Armed Forces of Ukraine) operation has successfully exploited seams of responsibility between the FSB (Federal Security Service), Rosgvardia (National Guard) and MoD (Ministry of Defence),” said Dara Massicot, a Russian defence scholar at the Carnegie Endowment for International Peace.

“I suspect targeted leaks will emerge between the MoD/GRU (General Staff of the Armed Forces of the Russian Federation) and the FSB over who is responsible for intel and defence failures,” she added.

Command and control – the exercise of authority by a commander over designated units, and what Nato militaries call “C2” – is crucial to operations, and has plagued the Russian army throughout the war.

This part of the border was particularly chaotic.

Unlike in the war zone inside Ukraine, the Russian chain of command on the border is hopelessly muddled.

The FSB’s border guard service has responsibility for the frontier. Internal defence is overseen by the Rosgvardia who are meant to back them up. They are separate agencies, and neither of them answer to the army or MoD.

For the army, Kursk is in the area of responsibility of the Moscow military district (MMD) commanded by Colonel General Sergey Kuzovlev. Most of its regular troops are now engaged in Ukraine.

The MMD, one of five military-administrative districts in Russia, is a new formation: it only came into being earlier this year when Vladimir Putin split the former Western military district in two in response to Nato expansion.

Alexei Smirnov, Kursk’s regional governor, is in charge of civilian evacuations, with the ministry of emergency situations chipping in.

No one has built a “Surovikin line”, or anything like the lines of trenches and minefields that defeated the Ukrainians in Zaporizhzhya last year.

Nor did anyone apparently notice that Ukraine began planning for the operation in March, with cross-border raids by Ukrainian-backed Russian rebel units.

“We did the same thing back in the day. We went in, observed the reaction – how quickly they respond to your arrival, how many forces are there, where, what, how – and then we left. Then again and again,” an ex-Russian officer who previously fought against Ukraine told the Russian outlet Important Stories.

“So, eventually, [the AFU] already had a plan, gradually pulled in troops in small groups so as not to make a large movement noticeable, and then just broke through.”

Despite six months of such warning signs, “f---ing nothing” was done to reinforce the border, he added.

When the “textbook” Ukrainian attack came on Tuesday last week, outnumbered FSB border guards and conscripted troops had to fight tanks and armoured vehicles with rifles. It is no wonder so many surrendered.

“The AFU planned everything smartly, like straight out of a textbook: conduct additional reconnaissance, chart the route, and most importantly, do it quickly,” the Russian rebel officer added.

“So they just push forward as fast as possible, while ours are talking s—, arguing, showing up, and filming reports. As they say in the army: ‘If you want to defeat Russia, declare war, and it will f— itself up with inspections.”

Ukrainian troops who have returned from the fighting, as well as Russian war bloggers, have described conscripts caught unawares and being killed or captured in large numbers.

The units rushed in to respond to the invasion were also a mixed bag. On the border were the FSB troops, many of whom were quickly captured.

The 810th separate marine brigade, part of the Black Sea fleet,  was redeployed either from the Kharkiv region, or the Pokrovsk front in Donbas, according to different military think tanks.

The Akhmat special forces, commanded by Ramzan Kadyrov’s right hand man, Apti Alaudinov, is technically under the control of the Rosgvardia.

The 128th Separate Motorised Rifle Brigade and the 15th Separate Motorised Rifle Brigade were both hit by Ukrainian Himars rockets while moving from different directions into Kursk.

The Centre for Defence Strategies, a Ukrainian think tank, named four more rifle brigades and regiments drawn from the Kharkiv and Zaporizhia fronts and two airborne battalions from the strategic reserves who are being rushed to Kursk.

What’s worse is that the main Russian formation facing Ukraine in this area is bogged down in an assault in the Kharkiv region that began three months ago.

“The Operational Group of Forces North received a name change and upgrade about one to two weeks before it attacked Kharkiv in May. 

“Prior to May it was a territorial defence group. So for the past three months it’s been transitioning from a defensive to offensive orientation, meaning that this Russian op group was much weaker than the others”, said Ms Massicot.

“From May to August it had a major reorganisation, a new commander, and attacked Kharkiv early. Its ministry of defence units are now bogged down in Kharkiv and that offensive is not making progress.”

The disaster has triggered open infighting.

Russian military bloggers accused the Chechen Akhmat troops of fleeing at the first sign of trouble, leaving poorly equipped and trained conscripts to bear the brunt of the assault.

Gen Alaudinov, the Akhmat commander, in turn told  Semyon Pegov, the Russian war blogger, that incompetent generals from the regular army were to blame for allowing the Ukrainians to “calmly withdraw” units from other parts of the line and concentrate them for the assault on Kursk.

He went on to take a swipe at “someone from the ministry of defence,” who he said “deceived, deceived, deceived so much they ended up deceiving themselves”.

He did not name the military official or officials he was referring to, or expand on the nature of the deception.

But a number of top Russian generals, including army chief Gen Valeriy Gerasimov, will be trying to convince Putin it is not their fault.

For the Ukrainians, a dilemma presents itself.

So far, Russia does not seem to have eased the tempo of its offensive in Donbas. That suggests one of the key goals of the Kursk offensive – drawing off Russian forces from that front – is yet to be achieved.

But keep pressing on into Russia, and they risk blinding success turning into devastating encirclement and defeat.

Dig in and hold ground, and they could be drawn into the kind of attritional trench warfare that favours Russia’s dominance in men and equipment.

Retreat, and they will relinquish the advantage of occupying Russian territory.

But they could claim a victory, take vast numbers of prisoners for exchange, and preserve the lives of their own troops.

Ukraine has kept the objectives of the offensive under wraps. But there are already signs of a plan emerging.

Ukrainian Telegram channels on Tuesday released videos of prisoners from Russian marine and army units who all asked, clearly under duress, to be exchanged for Azov regiment prisoners captured by Russia in Mariupol.

Bringing the Azov veterans home would be a major propaganda coup for Ukraine – and it is possibly one of the goals president Volodymyr Zelensky set for the operation.