Mines are wonderful, cheap, cheap things. You can litterally throw tens of thousand of them into the sea in a day or two. Any ship can do it: in the old Swedish cold war planning even all those big white cruise liners and the icebreakers where to be mobilized and filled with mines for preemptive mining if the risk of war became too great.

Clearing mines is boring, dangerous and very time-consuming. Not very fun to hang around clearing mines when someone might fire anti-ship missile from nondescript truck-launchers onshore either.

On top of this, mine countermeasures is the ugly bastard child of the US Navy. The mighty US Navy has 14 mine countermeausre vessels, compared to the 11 of the at-best midrange Royal Swedish Navy. To improve things even further, the US mine ships are in a really bad state.

Peak oil is not an energy crisis. It is a liquid fuel crisis.