Russia has had to demine the entrance to Sevastopol, it appears Ukraine have managed to get unmanned boats to seliver mines to the entrance and mine it.
In October 14, 2023, the russian Black Sea Fleet utilized mine-sweeping ships, including Vice-Admiral Zakharin, Ivan Antonov, Ivan Golubets, and Kovrovets, to conduct combat trawling to clear out sea mines in the outer roadstead of Sevastopol Bay, marking the first time since 1974 that such action was taken in russia.
This information was reported by the bmpd blog (available in public access), referencing the Morskoy sbornik monthly magazine from the russian Ministry of Defense, issue No. 12 (not available in public access).
To put it simply, the Ukrainian Defense Forces in an unknown way successfully deployed a significant number of sea mines in the area in October 2023, prompting an immediate need for combat trawling by the russian fleet.
And apparently, this episode was so sensitive that russians acknowledged the very fact of such an event only two months later.
Surface ships of the Ukrainian Navy can be ruled out as the source of mine deployment.
Just in case, we remind you that publicly available data indicates the Balta auxiliary ship was converted into a minelayer just months before russia's full-scale military invasion of Ukraine.
https://en.defence-ua.com/events/ukr...ones-8830.html