Engineer Combat Battalion
An Engineer Combat Battalion (ECB) was a designation for a battalion-strength combat engineer unit in the U.S. Army, most prevalent during World War II. They are a component of the United States Army Corps of Engineers. Also known as "Combat Engineer Battalions", they were typically divided into four companies: A, B, C, and Headquarters and Service (H&S).
Source: Wikipedia — Engineer Combat Battalion (CC BY-SA 4.0)