Relations between Nasser and Qasim grew increasingly bitter on 9 March, after Qasim's forces suppressed a rebellion in Mosul, launched a day earlier by a pro-Nasser Iraqi RCC officer backed by UAR authorities. Nasser had considered dispatching troops to aid his Iraqi sympathizers, but decided against it. He clamped down on Egyptian communist activity due to the key backing Iraqi communists provided Qasim. Several influential communists were arrested, including Nasser's old comrade Khaled Mohieddin, who had been allowed to re-enter Egypt in 1956.

What Iraqi leader clashed with Nasser?