Battlecruisers as global trade-defence cruisers

What was wrong with the all-battlecruiser idea?

Battlecruisers made sense for trade defence and hunting raiders, but they needed a balanced battleship force and should not have been treated as battle-line substitutes.

The type made sense as an enlarged armoured cruiser suited to protecting Britain's global trade and hunting hostile cruisers and surface raiders. In a world before reliable radar, mature radio systems, and carrier air power, speed and range gave that super-cruiser a clear strategic purpose. Fisher should, in this view, have paired a three-ship battlecruiser squadron with three modern battleships rather than allowing the cruiser idea to displace the battle line. The name battlecruiser then encouraged battleship-like expectations for a ship designed around a different mission. The alternative label dreadnought cruiser keeps the design connected to its cruiser ancestry and trade-defence role.