Heavier anti-aircraft guns did not solve U-boat vulnerability

The earlier 37 mm weapon had a poor reputation for reliability and struggled against the large aircraft encountered late in the war. Effective fire required coordinated crew work, with separate men controlling traverse, elevation and ammunition supply. Opportunities for practice were limited while the skies became more dangerous. Later twin 37 mm mountings performed better but reached relatively few boats. The 20 mm weapons were easier to aim, yet fast-moving aircraft remained difficult targets from a pitching submarine. A move away from surface anti-aircraft fighting towards submerged operation followed, although the assessment here doubts how completely the remaining fleet achieved that aim.