Vietnamese efforts to reach a permanent political settlement went nowhere during 1973. President Thieu pursued a policy known as the "Four No's": no negotiations with the communists; no coalition government; no loss of territory; and no communist activity in South Vietnam. North Vietnam faced some difficulties before fully renewing its war effort. Le Duan traveled to the Soviet Union and China in June 1973, seeking additional aid, but found the communist powers more interested in developing better relations with the United States than in North Vietnamese victory. North Vietnamese troops proceeded to their main objective, Ban Me Thuot in the central highlands. They attacked on 10 March and captured the city four days later. Other forces advanced toward Pleiku and Kontum. South Vietnamese losses in the central provinces led Thieu on 13 March to order a military withdrawal to a defensive line just north of Saigon, abandoning the northern portion of his country.