A suicide bomber launched the third major attack in five days when he blew himself up at an Iraqi army base in the city of Taji, 20 miles north of Baghdad, on Monday morning. At least 11 people were reported killed at the entrance to the base where a jail housing Al-Qa’ida prisoners is located. The ability of Iraq to protect its citizens when the last of the American forces leaves at the end of the year continues to be underscored by the surging violence.