The line was a success and provided a major portion of Mauritania's GDP; as a result, the line was nationalized in 1974.[1] Following Mauritania's annexation of southern Western Sahara in 1976, the line came under constant attack by Polisario militia, effectively putting the line out of use and thereby crippling Mauritania's economy.[1] This played a major role in prompting the army to overthrow Mauritanian President Moktar Ould Daddah in 1978, followed by a withdrawal from Western Sahara the following year. With the line now secure, repairs were conducted and trains starting using it once again in the early 1980s.[1] This railway is unusual for its usage of the Soviet type coupler SA-3, which is quite rare in non ex-Soviet countries.[citation needed]