Feb 21, 11:18 PM (ET) By NEDRA PICKLER ATLANTA (AP) - Democratic presidential candidate John Kerry accused President Bush on Saturday of using surrogates to attack his military service in Vietnam and his subsequent activism against that war. In a letter to Bush, Kerry wrote: "As you well know, Vietnam was a very difficult and painful period in our nation's history, and the struggle for our veterans continues. So, it has been hard to believe that you would choose to reopen these wounds for your personal political gain. But, that is what you have chosen to do." Kerry was reacting...