When was the location 15km NW of Pol-E Khomri, the circumstaances IED and the casualties of 1 WIA?
CREATE TABLE "2011" (
  "date" text,
  "location" text,
  "nature_of_incident" text,
  "circumstances" text,
  "casualties" text
);
SELECT "date" FROM "2011" WHERE "casualties"='1 wia' AND "circumstances"='ied' AND "location"='15km nw of pol-e khomri';