Russia's extensive systems of military defensive works suggest "deep concern" over a major Ukrainian breakthrough, the U.K. Defense Ministry reported on May 1.
According to the ministry, Russia has, since summer 2022, set up "some of the most extensive systems of military defensive works seen anywhere in the world for many decades."
Russia has made a "particular effort" to fortify its defenses around the northern border of Crimea, which has been under occupation for nine years, according to the ministry.
Russia has also dug "hundreds of miles" of trenches both in occupied Ukrainian territory and "well inside" Russian territory, including Belgorod and Kursk oblasts, the ministry said.
In addition to fears of a Ukrainian breakthrough, the defensive measures are likely also "attempts to promote the official narrative that Russia is 'threatened' by Ukraine and NATO," the ministry wrote.
Ukraine is expected to launch a major counteroffensive in the coming weeks. The long-awaited counteroffensive is seen as a critical juncture to take back Ukrainian territory under Russian control.
Deputy Defense Minister Hanna Maliar said on national television on April 19 that "complex measures" of Ukraine's planned counteroffensive are "already underway" in the east.