Sweeney left active duty with the rank of lieutenant colonel on June 28, 1946, but remained active with the Massachusetts Air National Guard. Later promoted to full colonel, on February 21, 1956, Sweeney was named commander of its 102nd Air Defense Wing and shortly after, on April 6, was promoted to brigadier general. During this time, he was activated with the 102nd and served in Europe during the Berlin Crisis from October 1961 to August 1962. Sweeney was made chief of staff in October 1967.