Russia has been waging war in Ukraine for a little over two months now. That’s not an especially long time. The Korean War lasted for three years, World War II for six. The Arab-Israeli wars, on the other hand, took only a matter a matter of days.
A variety of factors contribute to a war’s duration. The size of the battlefield is just one. The smaller the battlefield, the fewer soldiers can fit on it and, generally, the shorter the war. In Ukraine, the battlefield is substantial. On that criterion alone, the war there might last for years.
As important are the forces arrayed against each other. All three axes of Russia’s initial attack – against Odesa, Luhansk and Kyiv – broke because of logistical difficulties. The lines of attack were built largely around infantry with supporting artillery and airstrikes, but the primary strategic principle remained the same. They continued to try to seize cities rather than destroy the Ukrainian army. Thus, about a month after Moscow ruled out Kyiv as a primary target, it has yet to eliminate resistance in the east and south. Part of this has to do with the fact that cities are difficult battlefields. The advantage goes to the defender, who knows the city well and can formulate a strategy around that knowledge.
However, the continued problem for Russia is that rather than concentrating its forces on one critical target in order to create optimal circumstances for a victory before moving to another target, it is still driven by its primary mission and vision, much of which is predicated on the assumption that the Ukrainian army is an insignificant force that can be defeated in the course of pursuing its primary strategy: seizing cities. Indeed, the idea of seizing cities as the operational task comes from the Russian goal of conquering all of Ukraine. In pursuit of that goal, there is a logic to defeating the Ukrainian army and occupying cities.
But Moscow miscalculated the initial problem. Ukraine is big, and its forces fought from dispersed and tactically mobile positions, the exact kind of defense Russia is ill-suited to fight. The Ukrainians could decline combat where they chose and engage at the time of their choosing. Russia had tons of armor, but armor is not so useful against dispersed infantry or in cities.