 This is partly due to the Battle of Hampton Roads, in which the Union turreted ironclad and the Confederate casemate ironclad (sometimes called the "Merrimack") dueled, giving rise to the popular notion that "The North had "Monitors" (predominantly deployed for coastal operations, whereas the unseaworthy Union casemate ironclads were restricted to inland river operations – hence their "brown-water navy" nickname) while the South had (casemate) ironclads".In effect, the Confederacy concentrated its efforts on casemate ironclads as a means to harass the Union blockade of their ports, but this was a choice dictated by available technology and materials rather than by confidence in the possibilities of this type.Since breaking the Union blockade was the primary objective of the Confederacy's casemate ironclads, as outlined in a May 1861 letter from its Secretary of the Navy Stephen Mallory (who was the one who came up with the idea of employing ironclads to offset the numerical superiority of the Union Navy in the first place) to the Confederate House Committee on Naval Affairs, the majority of them were from the outset designed to operate in coastal waters as well as inland waters, and unlike their Union counterparts were, theoretically at least, seaworthy to a limited extent – since they were never expected to venture out onto the high seas.