The US and Kurdish authorities in Iraq on Tuesday issued a joint ultimatum for all groups in the north of the country, other than the two main Kurdish parties, to give up their heavy weapons. This extends a new weapons regime that came into force in the rest of Iraq on Sunday, but its implementation faces a special challenge in a mountainous region that was outside the control of the Baghdad regime after 1991 and where many factions have substantial arsenals. The order - which lists a number of proscribed weapons including the BKC machine-gun, the Dushka anti-aircraft gun, rocket-propelled...