Radar changed both detection and deception for small craft

How did radar, hydrophones, and the absence of comparable sensors affect small-craft night fighting?

Sensors improved detection, but radar emissions could reveal a fragile boat to enemy receivers or aircraft and could also be used deliberately to steer an opponent into an ambush.

Allied industrial capacity made it easier to adapt destroyer equipment for sloops and corvettes or develop compact radar and hydrophone sets for motor boats. The broader hulls of many escorts could accept equipment that was awkward or top-heavy, while the smallest craft needed purpose-built systems. Radar could locate an opponent at night, yet its emissions could warn that opponent, allow it to avoid contact, or attract aircraft against an unarmored boat. Japanese small combatants lacked an equivalent radar-development base, creating a different tactical problem from the heavily equipped Allies. That vulnerability could itself become a tactic: one transmitting boat might herd an enemy toward other torpedo boats waiting in ambush.