The primary challenge for Ukrainian forces is the continued difficulty of breaking through Russia’s multi-layered defensive lines in the eastern and southern parts of the country, which are marked by tens of thousands of mines and vast networks of trenches. Ukrainian forces have incurred staggering losses there, leading Ukrainian commanders to hold back some units to regroup and reduce casualties.
“Russians have a number of defensive lines and they [Ukrainian forces] haven’t really gone through the first line,” said a senior Western diplomat.