The major dust-up was the Yemeni civil war (which has returned during the so-called Arab Spring); Nasser’s Egypt backed a socialist faction, and the Saudis backed some jihadists. Egypt used gas warfare against Saudi troops/proxies in that war, the only time since WWI I can think of that poison gas has been used on a battlefield, other than Saddam’s use of it against the Kurds.
In 1970, Syria conducted a short-lived invasion of Jordan in support of the attempted PLO overthrow of King Hussein. Israel flew sorties to buzz the tanks, and the Syrians turned tail. That may have paid dividends in 1973, when King Hussein passed the exact date of the upcoming Arab war against Israel — unfortunately the information was ignored. Anyway, in 1970 the Jordanian army kicked the living crap out of the PLO, such that PLO “soldiers” fled to the border and surrendered themselves to the Israelis just to get away.
Syria also invaded Lebanon and proceeded to occupy it for decades; Lebanon has been in civil war off and on since the 1950s, but the latest mess began thanks to the PLO’s entering Lebanon, setting up armed camps, and destabilizing the gov’t.
The self-identified “Mahdi” organized a takeover of the Grand Mosque in Saudi Arabia, resulting in a lot of dead Muzzies on both sides. After the Saudis finally gathered the firepower, manpower, and internal political support to storm the place (the Wahhab clerics weren’t going to give their okay to the dynasts, and extracted some concessions from them) they killed many of the followers of that nutbag. Interestingly, some of the survivors were US citizens, and were held for a little while, then deported here, i.e., repatriated.
Anyway, sorry if this reply is duplicative, I started it, had unexpected company, then headed for the store, and wound up taking a walk, was gone a few hours between the above and this.
The Japanese used it in the Second Sino-Japanese War, and the Iraqis used it in the war against Iran.