FORWARD OPERATING BASE MAREZ, Iraq - Hunched and haggard, Sgt. Evan Byler hobbled around his camp in Northern Iraq yesterday, wondering how a suicide bomber could have infiltrated the chow hall. "It's kind of a shock that something like that was allowed" on the base, said Byler, a Fauquier County resident and member of the Richmond-based 276th Engineer Battalion. "It is something we have been trying to prevent." "Basically, everyone is going to have to step up their alertness and have an eye out for anything suspicious. Home is coming up, but we still have a long way off." Byler...