The 4.7 inch QF Mark IX and Mark XII were 45-calibre, 4.7-inch (120 mm) naval guns which armed the majority of Royal Navy and Commonwealth destroyers in World War II,[1] and were exported to many countries after World War II as the destroyers they were mounted on were sold off.

[6] Admiral Sir Philip Vian describes the use of Tribal-class destroyer mounted Mk XII guns against aircraft during the campaign in Norwegian waters, from April to June 1940: It became clear at once that in an attack from the air in narrow waters flanked by mountains, the cards were held by the aircraft.

The daylight passage of the convoy and escort through this waterway, speed five knots, on a steady course and with mountains rising steeply either side, presented an alluring invitation to enemy aircraft.

Junkers attacks persisted to the end, but the fire of the destroyers, although limited to an elevation of forty degrees, was enough to keep the enemy just too high for their standard of marksmanship.

[8][9] Savage was the exception in this respect, being fitted with 4.5 inch calibre; a twin mounting forward and two singles aft.