An Iraqi soldier securing an area where a gunfight erupted between gunmen and Iraqi forces in Basra in January.Credit...Essam Al-Sudani/Agence France-Presse — Getty Images BASRA, Iraq � This southern port city has been, in effect, on its own since September, when British forces here moved to the outskirts, yielding authority to local leaders. British and American officials say Basra’s experiment i