When naval ships need ice strengthening

How many naval ships should be rated for icebreaking?

The number depends on geography and mission: navies that routinely operate among ice need many, while others should avoid the extra hull weight and expense.

A navy regularly surrounded by ice needs enough suitably rated ships to keep operating there. Strengthening the hull adds weight and expense, with consequences for the rest of the design. A navy that rarely encounters ice has less reason to accept those costs. Sweden provides the immediate example of a navy whose geography makes the requirement relevant.