Meanwhile, a new paramilitary organisation gained prominence in Iran, the Islamic Revolutionary Guard Corps (often shortened to "Revolutionary Guards", and known in Iran as the "Sepah-e-Pasdaran"). This was intended to protect the new regime and counterbalance the army, which was seen as less loyal. Despite having been trained as a paramilitary organisation, after the Iraqi invasion, they were forced to act as a regular army. Initially, they refused to fight alongside the army, which resulted in many defeats, but by 1982, the two groups began carrying out combined operations. Another paramilitary militia was founded in response to the invasion, the "Army of 20 Million", commonly known as the Basij. The Basij were poorly armed and had members as young as 12 and as old as 70. They often acted in conjunction with the Revolutionary Guard, launching so-called human wave attacks and other campaigns against the Iraqis. They were subordinate to the Revolutionary Guards, and they made up most of the manpower that was used in the Revolutionary Guard's attacks. Stephen Pelletiere wrote in his 1992 book "The Iran–Iraq War: Chaos in a Vacuum":  The most important dispute was over the Shatt al-Arab waterway. Iran repudiated the demarcation line established in the Anglo-Ottoman Convention of Constantinople of November 1913. Iran asked the border to run along the thalweg, the deepest point of the navigable channel. Iraq, encouraged by Britain, took Iran to the League of Nations in 1934, but their disagreement was not resolved. Finally in 1937 Iran and Iraq signed their first boundary treaty. The treaty established the waterway border on the eastern bank of the river except for a anchorage zone near Abadan, which was allotted to Iran and where the border ran along the thalweg. Iran sent a delegation to Iraq soon after the Ba'ath coup in 1969 and, when Iraq refused to proceed with negotiations over a new treaty, the treaty of 1937 was withdrawn by Iran. The Iranian abrogation of the 1937 treaty marked the beginning of a period of acute Iraqi-Iranian tension that was to last until the Algiers Accords of 1975. The 1974-75 Shatt al-Arab clashes were a previous Iranian-Iraqi standoff in the region of the Shatt al-Arab waterway during the mid-1970s. Nearly 1,000 were killed in the clashes. It was the most significant dispute over the Shatt al-Arab waterway in modern times, prior to the Iran–Iraq War.