ISLAMABAD, Pakistan, March 6 -- NATO and Afghan forces on Tuesday launched what commanders described as a major operation in a key province of southern Afghanistan, part of a bid to win back territory that has become a haven for insurgents. The operation, the international force's largest to date in the country, was centered in the northern part of Helmand province, where Afghan government authorities have little control and insurgents move with relative impunity. The province's governor said Tuesday that 700 al-Qaeda fighters had moved into the region, and were believed to be planning more of the suicide bombings and...