An extra gun deck increases the volume of fire and gives a ship a height advantage over a smaller opponent. Higher batteries can fire down onto exposed decks and clear the gun crews serving there. The attacking crews can deliver that fire from protected positions within their own ship. A two-decker has this advantage over a single-decker, and a three-decker can repeat it against a two-decker. At Vyborg, that helps explain why Sweden's ships face a difficult individual match against Russia's 100-gun first rates.
Notable Point · 50:55-52:45
An extra gun deck improves firepower and crew protection
A three-decker can fire down onto a two-decker's exposed decks while its own gun crews work from protected positions.