Ukraine is outmatched by Russian forces and requires significantly more infantry and weapons if it hopes to win the war, according to military intelligence and independent battlefield monitors. Although Moscow is paying an extraordinary price for comparatively minimal gains, western officials believe the country can sustain at least another year of war at the current rate of attrition. On Tuesday it will be four years since Russia began its full-scale invasion of Ukraine. After months of incremental advances, it appears to be on the verge of capturing a series of strategic locations in Ukraine’s so-called “fortress belt” and is expanding...