Japanese planners assembled detailed information on the canal and identified the Gatun Locks as the more damaging target, while Miraflores was considered more vulnerable to bombing. The plan called for I-400, I-401, I-13, and I-14 to launch ten Seirans from off Ecuador on a moonlit route toward the Caribbean side. The moonlit launch and dawn approach invite comparison with the British attack on Taranto in 1940, although this plan depended on submarine-delivered aircraft crossing South America. Flying without floats, the aircraft would cross the continent at about 13,000 feet, use the lights of Colón as a navigation point, and approach the locks near dawn. An intended mix of torpedo and bomb attacks became an all-bomber plan after only one pilot mastered the torpedo technique, with the crews then due to ditch beside the submarines for recovery. Blueprints and construction knowledge supplied by a Japanese engineer gave the Naval General Staff unusually detailed evidence for choosing where damage would be hardest to contain.
Chapter · 46:29-50:50
The planned attack on the Panama Canal
The planned Panama Canal operation shows how the I-400 force was meant to turn its range into a strategically disruptive strike.