The DB-3 record has a 1939 Japanese gap

The closing investigation begins with an absence rather than a claimed operation. The DB-3 entered service before 1939 and later remained active for years, while its record includes Chinese use against Japan and Soviet use against Finland and Germany. No account was found of Soviet DB-3 employment against Japan during the 1939 border conflict. That omission matters because it tests whether paper range and nominal availability had become deployable maritime air power.