war-devastated area; war-damaged district
Refers to a geographical area or district that has been heavily damaged or destroyed by war. Often used in historical or reconstruction contexts.
After the war, the reconstruction of war-devastated areas was urgently pursued.
This whole area was once a war-damaged district.
被災地 is a broader term for any disaster-stricken area (natural or man-made), while 戦災地区 specifically refers to war damage.
Compound of 戦災 (war damage) and 地区 (district, area).