By the late 1960s, the build-up of Iranian power under Shah Mohammad Reza Pahlavi, who had gone on a gargantuan military spending spree, led Iran to take a more assertive stance in the Near East [REF].
The Shah justified his move by arguing that almost all river borders all over the world ran along the thalweg, and by claiming that because most of the ships that used the Shatt al-Arab were Iranian, the 1937 treaty was unfair to Iran [REF].