Passage: In March 1937, a design team headed by Donald Douglas, Jack Northrop, and Ed Heinemann produced a proposal for a light bomber powered by a pair of 450 hp (336 kW) Pratt & Whitney R-985 Wasp Junior radial engines mounted on a shoulder wing.It was estimated that it could carry a 1,000 lb (454 kg) bomb load at 250 mph (400 km/h). Reports of aircraft performance from the Spanish Civil War indicated that this design would be seriously underpowered, and it was subsequently canceled.

Question: What war were the reports from?
Spanish Civil War