Russia net-lost 100 square miles of Ukrainian territory over four weeks (28 April to 26 May), including 38 sq mi in the week of 19-26 May, according to ISW data compiled by Russia Matters at Harvard's Belfer Center. Russia's operational pattern since the full-scale invasion has been incremental advance punctuated by Kursk-style reversals; a four-week sustained net-loss run is something else.
The net advance rate collapsed 94% year-on-year, from 1,619 sq km in January-May 2025 to 104 sq km in the same window of 2026. Seasonal factors cannot account for that. It tracks the period of Ukraine's most intensive drone campaign against Russian logistics and training infrastructure.
For Russia's defence establishment, the data bites. The 2026 defence budget of 13.5 trillion rubles was calibrated on higher advance rates. At current attrition and territorial costs, each ruble buys less than a fifth of the territory it bought in 2025.
NATO Secretary General Mark Rutte said on 21 May that Ukraine's defences are "stabilising the frontline," the closest the Alliance has come to acknowledging a Ukrainian operational advantage. ISW recorded Russia's first net monthly loss since the August 2024 Kursk incursion , then 12 sq mi lost in 5-12 May and 29 sq mi in 12-19 May ; the four-week figure extends that reversal to its deepest point.
