In the last two weeks we have witnessed two important developments in the war in Ukraine. First, after launching a series of combined arms attacks against Russian defences in the north east of their nation, the Ukrainian Army was able to rapidly penetrate Russian positions and then conduct a rampaging exploitation that carried them to the banks of the Oskil River.

The second important development has been the 21 September speech by Russia’s President Putin that decreed a ‘partial mobilisation’ of he Russian military. This was followed by statements by the Defence Minister Shoigu that this would comprise the indication of up to 300,000 reservists, and the halting of discharges of Russian contract military personnel.

At the time of writing, the impact of the Russian partial mobilisation remains to be seen. But the Ukrainian offensive is continuing to exploit a bumbling and incoherent Russian defensive scheme to the east of Kharkiv. Thousands of square kilometres of Ukrainian territory have been recaptured, and many towns and their inhabitants have been liberated from the depredations of a brutal occupying group of Russian Army, Wagner Group and proxy thugs. Even the Oskil River defensive line, rapidly established by the Russians, appears to be crumbling.

Ukraine clearly achieved surprise against the Russians in the Kharkiv region. This is an important principle of war. For any military commander or theorist, achieving surprise is the acme of the military art.

Deception and operational art have been central to Ukrainian preparations for their achieving surprise against the Russians in this new phase of the war.

That it was able to exploit this opportunity indicates that Ukraine had an excellent plan to deceive Russian aerial and satellite intelligence collection capabilities, as well as their tactical reconnaissance and surveillance. As one military interlocutor in Kyiv confirmed to me last week, Russian tactical reconnaissance in the east of Ukraine has been poor. It has generally consisted of ‘advance to contact’ with infantry and armour, rather than through the use of dedicated air and ground reconnaissance assets. This means that the environment is ripe for tactical and even operational surprise, something the Ukrainians clearly recognised in their planing for the Kharkiv offensive.

While the Russian focus was holding on in the south, and conducting small scale attacks in the Donbas, Ukraine planned and launched an operation in the north.

This is not to suggest that Ukraine’s operations in the south were a feint. They were not, and this was recently confirmed to me by a senior Ukrainian military planner during my visit to Kyiv. The north and south are mutually supporting offensives in a larger Ukrainian operational design. This is the second important aspect of the Ukrainian preparation and execution of it is Kharkiv offensive.

Operational design is an important component of military professionalism. Through good operational design, military commanders and their staffs’ sequence and orchestrate tactical goals and actions to meet desired strategic and political outcomes. Importantly, much of the prioritisation for allocation of forces, logistic support, intelligence, transport, and multi domain collaboration is undertaken as part of operational planning. Ironically, it was the Russians in the early twentieth century who were early advocates for such thinking about military operations.

For the Ukrainians, their operational design for the concurrent south and north eastern campaigns will have considered the desired outcomes and worked backwards from there. These outcomes would have included political aims (both domestic and international) and military.

Ensuring they had a design to achieve these outcomes would have required the Ukrainians to war game different designs that considered various numbers of concurrent or sequential offensives. And time is a central consideration for operational design activities.

The ability to exploit time is one of the most important considerations in the planning and execution of military campaigns. The Ukrainians would have carefully analysed the best times to conduct their offensives. It would have been based on intelligence on Russian defensive dispositions, the location and quantities of Russian forces held in reserve, as well as logistics and key supply routes. And like all major military activities, there would have been a political dimension to timing.

What might this mean in the weeks ahead?

The two concurrent Ukrainian offensives have totally compromised the Russian operations in the Donbas. The capture of the key transportation hub of Kupiansk particularly hurts the Russians. It compromises Russian supply routes and introduces a larger psychological issue with Russian soldiers and commanders fighting in the east.

It will also be difficult for the Russians to continue to fight in the east without responding to the threat that the Ukrainians now pose to their rear areas and logistics. This problem will only get worse if the Ukrainians are able to continue their advance across the Oskil River and deeper in Luhansk. To respond, the Russians will have to reorient their forces in the east, and possibly pull troops from the south. This effectively kills any Russian offensive capability across the east and south, while it also creates other opportunities for Ukraine.

Because of this Russian reinforcement ‘shell game’, it is possible that we could see cascading Russian tactical withdrawals and failures in various regions as a consequence.  This, and the resulting losses in equipment and personnel, compromises Russia’s capacity to dictate the pace and location of operations henceforth.

Having surprised the invader, the Ukrainian army has generated shock among Russian troops and commanders. This period of shock is generally a productive time for those on the offensive. It is when they can seize the most ground, and destroy the largest number of enemy troops. And it is exactly what the Ukrainians are doing. The Ukrainians, using mission command, are operating inside the Russian tactical and operational decision cycles.

This shock extends well beyond the battlefield. Russian military bloggers, initially reticent to accept Ukrainian gains, have been scathing about Russian military performance and have called for national mobilisation. Putin was criticised publicly by the Indian prime minister at the recent Uzbekistan summit. More prominent Russians, including famous singer Alla Pugacheva, have called for an end to the war.

There are some tactical and operational risks for Ukraine as it continues this offensive. A Russian counterattack might block or ‘pinch off’ the penetration and isolate the advancing Ukrainian ground forces. But the Russians need to move quickly to do this and may not have sufficient reserves to do so.

The Russians, while in deep strife, retain a formidable presence in Ukraine. Luhansk, large parts of Donetsk and southern Ukraine (including Crimea) are still occupied by the Russians. More Ukrainian offensives will be necessary to eventually the Russians from these areas. President Zelensky has promised as much in his 18 September daily speech.

The Russian partial mobilisation will likely be consumed by reinforcing the existing presence in Ukraine. Most Russian units have been fighting there for seven months. Historical evidence points to a drop off in combat efficiency after 3-4 months. The Russians must replace and rotate out exhausted combat forces. It is unlikely that this mobilisation will see an expanded offensive capacity from the Russians at least until 2023. Even if they are able to generate offensive capacity, the size of the mobilised force is unlikely to be sufficient to change the current trajectory of this war; the Ukrainians simply have more personnel available to fight, and they are much more motivated to do so.

After nearly eight months of bitter fighting, Ukraine now has the initiative in this war. Importantly, it now also has the tactical and operational momentum as the winter approaches. This is why Moscow felt it had no choice but to conduct their partial mobilisation. The Ukrainian government and high command of the Ukrainian Armed Forces will be keen to exploit their momentum before mobilised Russian reinforcements arrive.

And while the light at the end of the tunnel may have dimmed due to the Russian mobilisation announced this week, the Ukrainian army is pushing on with grim determination to win this war. Every senior Ukrainians I spoke to during my visit believes they will prevail over the Russian invaders. It is likely that they will win, but probably at a greater cost than anticipated before the Russian mobilisation announcement.