Operation Masher/White Wing/Thang Phong II launched - Jan 24, 1966 - HISTORY.com

In the largest search-and-destroy operation to date–Operation Masher/White Wing/Thang Phong II–the U.S. 1st Cavalry Division (Airmobile), South Vietnamese, and Korean forces ssweep through Binh Dinh Province in the central lowlands along the coast.

The purpose of the operation was to drive the North Vietnamese out of the province and destroy enemy supply areas. In late January, it became the first large unit operation conducted across corps boundaries when the cavalrymen linked up with Double Eagle, a U.S. Marine Corps operation intended to destroy the North Vietnamese 325A Division. Altogether, there were reported enemy casualties of 2,389 by the time the operation ended.

Also on this day: Defense Secretary Robert McNamara, in a memorandum to President Johnson, recommends raising the number of U.S. troops in Vietnam to more than 400,000 by the end of the year. However, he warned that planned deployments and increased bombing would not ensure military success. Ultimately, McNamara was correct and the war raged on even as total U.S. troop strength in country went over 500,000 soldiers in 1969.