afghanistan signed a treaty of friendship with iran in 1921, when the country was ruled by king amanullah khan and iran was still under the qajar dynasty. in september 1961 ties between two countries were broken off and resumed in may 1963. prior to 1979, the year in which both iran underwent the iranian revolution and afghanistan was invaded by the soviet union, the issue of water rights of the helmand river were an issue of great importance between the two nations. disputes over the helmand water are noted in the 1870s, flaring again after the river changed course in 1896. in 1939, the kings of the two countries signed an accord to share water rights, which was signed but never ratified; this was repeated in 1973 with a treaty between the prime ministers of both nations, and again not ratified. according to reuters report, in 2018 afghan forces accused iran of presenting the talibans with arms and money even though iran denies this accusation.