Fidler's article may be behind a paywall but here's a summary:
Mis-estimations: Almost everyone, including the Russians, overestimated Russia's military capabilities and underestimated Ukraine's. An operation that was supposed to take a few days or weeks has lasted a year and the Russians have been devastated. They've lost approximately 200,000 men killed or wounded and almost half of their tank force.
Like external analysts, Moscow overestimated its own capabilities and underestimated how much Ukrainian military capabilities had improved since Russia first occupied Ukrainian territory in 2014. Mr. Putin failed to anticipate Western unity in backing Ukraine. And military planners sent in too small a force to take and occupy a country nearly the size of Texas.In return for this high cost they've gained almost nothing in terms of territory.
Morale: Napoleon considered the morale of an army to be much more important that manpower and equipment. If this is true the Russians are in serious trouble because the morale of most of their troops is very low whereas that of the Ukrainians is so far very high.
Russian troops are stuck with poor military leadership, badly maintained equipment and poor quality food and clothing. Many of the conscripts now in the battle are poorly trained and treated miserably by their officers.
Part of what has buoyed Ukrainian morale is the fact that early on, President Volodymyr Zelensky declined President Biden's offer to fly him to safety because the Russians planned to execute him. Zelensky chose to stay with his troops and much of his government stayed with him which inspired his troops to fight all the harder.
Planning: Russian president Vladimir Putin fully expected to roll into Kyiv with almost no opposition, but as soon as the tank columns moved across the border they were subjected to devastating attacks from Ukrainian forces. After that there didn't appear to be any Plan B and the Russians have been suffering terrible losses as they seek to regain the initiative.
One analyst cited by Fidler said he believed people had been fooled by U.S. military capabilities in our recent conflicts and our effectiveness in choreographing complex military operations. “They were given an unrealistic view of how war operates because of U.S. capabilities,” he said.
Intangibles: Here's Fidler:
That is partly because war is highly complex. Both the Russian and Ukrainian militaries have aspired to so-called combined arms warfare in which they try to orchestrate movement on the battlefield combining elements including armored vehicles such as tanks, infantry, artillery, air defense, engineering, communications and electronic warfare.Defense Is Easier: An invading force has to maintain longer supply lines and operate in the midst of a hostile population, both of which make success more difficult. As Fidler notes:
Ukraine has enjoyed the most success in combining these elements. Ben Barry, an expert in land warfare at the International Institute of Strategic Studies in London, said Kyiv had also “firmly demonstrated that both drones and counterdrone defenses are also part of combined arms.”
The Ukrainians, Mr. Cohen said, have shown two important, if less-measurable, qualities: the ability to adapt and the ability to move quickly. “You’re seeing that repeatedly demonstrated with the Ukrainians with their ability to incorporate all kinds of equipment that by normal peacetime standards, you would have thought that would take a very long time,” he said.
The Ukrainian military has been able to use dozens of types of disparate military equipment it has been given during the war by the West, many of which require separate training, and maintenance and logistics pipelines. It has also made better use of new commercial technologies.
Part of this success has come from Ukraine’s ability to devolve military decision-making down the chain of command to junior officers and noncommissioned officers in the field in contrast with the top-down direction of Russian forces, which has slowed decision making and made it harder for Russian forces to adapt to changing facts on the ground.
Russia’s advance on Kyiv early in the war suffered just this problem as tanks stretched out on the road to the Ukrainian capital moved ahead of their logistics chain, cutting access to fuel and other supplies. Some Russian tanks were abandoned by their crews without fuel.Technology: He closes with this:
In many ways, the conflict in Ukraine is the most visible in history, both to the outside world and to military commanders. That is thanks largely to newer technologies including drones that fly over the battlefield revealing enemy positions, and intelligence from commercial and military satellites. Even everyday smartphones are throwing light on the battlefield, creating a vast archive of so-called open-source intelligence on the conflict.
Ukraine may have better eyes on the battlefield. In a report last week, the IISS said space had been “an enabler” for Ukraine through external commercial and military support “while Russian limitations in the domain have become apparent.”
Overall, said [one analyst].... “What we have now is an interesting war of very strong intelligence…You should have a pretty good idea about where units are. It’s the most visible battlefield that there’s been. I can’t think of anything that compares to it.”