Passage: In 1906, the commissioning of HMS Dreadnought brought about the obsolescence of all existing battleships. Dreadnought, by scrapping the secondary battery, was able to carry ten 12-inch (305 mm) guns rather than four. She could fire eight heavy guns broadside, as opposed to four from a pre-dreadnought; and six guns ahead, as opposed to two. The move to an 'all-big-gun' design was a logical conclusion of the increasingly long engagement ranges and heavier secondary batteries of the last pre-dreadnoughts; Japan and the United States had designed ships with a similar armament before Dreadnought, but were unable to complete them before the British ship. It was felt that because of the longer distances at which battles could be fought, only the largest guns were effective in battle, and by mounting more 12-inch guns Dreadnought was two to three times more effective in combat than an existing battleship.

Question: what was the improvement of the guns?
scrapping the secondary battery