Four days after Hurricane Katrina struck, the National Guard arrived in force Friday with food, water and weapons, churning through the floodwaters in a vast truck convoy with orders to retake the streets and bring relief to the suffering. "The cavalry is and will continue to arrive," said Lt. Gen. Steven Blum of the National Guard. At the New Orleans Convention Center, some of the thousands of storm victims awaiting their deliverance applauded, threw their hands heavenward and screamed, "Thank you, Jesus!" as the camouflage-green trucks and hundreds of soldiers arrived in this increasingly desperate and lawless city. "Lord, I...