What was the complement for the unit that had 3 off 37 men killed?
CREATE TABLE "table1_2596811_12" (
  "unit" text,
  "commander" text,
  "complement" text,
  "killed" text,
  "wounded" text,
  "missing" text
);
SELECT "complement" FROM "table1_2596811_12" WHERE "killed"='3 off 37 men';