There were informal pressures to prevent #greece and #turkiye going to war with each other - as they came close to at times in the 1960s and 1970s. these worked - in part because the #us was behind the policy and also because the two had a very rough military parity. I do not think there was an actual clause. The last country to attack an ally while still in formal alliance with it was #germany attacking #hungary in the summer of 1944 .