Armour protection only makes sense at a stated range

Could 11- and 12-inch guns defeat Grand Fleet armour schemes?

Potentially at the right range, but armour effectiveness must be judged against the engagement distance and the ship's intended tactical role.

Penetration depends on the engagement range as well as calibre and armour thickness. British battlecruisers were intended to use speed and distance as part of their protection, whereas German battlecruisers accepted a different balance for close support of the battle line. Even a six-inch gun could penetrate formidable armour if it fired from close enough. A weapon that penetrates at 10,000 yards does not necessarily invalidate protection intended for an 18,000-yard engagement. The film The Battle of the River Plate illustrates the point through Harwood's demand to close the range against Graf Spee. The film scene is an illustration, with the historical ships described as already being closer.