“I guess 18 months in Kharkiv wasn’t enough time to build fortifications.”
Longer than that. They had time since 2014 when Russia stole the Crimea and stirred up trouble in the Donbas. Yet they did very little or nothing at all.
Ukes have time to spare:
https://youtube.com/shorts/_gpNaTlWrA8?si=1Tjz_p1A02kGZ4SZ