https://www.csis.org/analysis/ukraines-offensive-operations-shifting-offense-defense-balance
This article sums the military situation up excellently. Free to read.
first and last paragraphs, but the middle's where the meat is ofc.
The IssueRussian fortifications in Ukraine are the most extensive defensive works in Europe since World War II, according to new CSIS analysis. The Russian military has constructed trenches, minefields, dragon’s teeth, and other barriers to slow Ukrainian forces during offensive operations. But as a review of previous wars shows, fortifications and other measures do not guarantee that the defender has the advantage. The Ukrainian military could effectively use a combination of strategy, technology, geography, and other factors to retake territory illegally seized by Russia.
Next Steps
The next phase of the war will hinge, in part, on the ability of Ukrainian forces to retake territory by moving from attrition to maneuver warfare and to shift the offense-defense balance in favor of the offense. As Napoleon wrote, “The strength of an army, like power in mechanics, is estimated by multiplying the mass by the velocity.”[52] A Ukrainian maneuver strategy places a premium on the second factor—velocity. Russian forces have attempted to shift the advantage to the defense and retain the territory they have conquered in Ukraine by constructing a formidable system of fortifications. But Russia faces several challenges in holding this territory, including weak ground forces that have not performed well on the battlefield, the need to defend a massive amount of territory, and variable construction of the fortifications.
This war is far from over. Western aid—including weapons systems, technology, training, intelligence, and financial support—will be critical over the long run to help Ukraine retake its territory and prevent Russia from invading again in the foreseeable future. The future trajectory of the war will also depend on whether Ukraine can exploit Russian vulnerabilities and effectively integrate technology, a clever strategy, force employment, nationalism, and other factors to turn the tide.