ArmyContinued from Page 1)3rd Brigade encountered aggressors” in mock combat today, climaxing two days of battalion field training.This brought the Pennsylvania National Guard division’s two-week training here and at Camp Pickett, Va., to the midway point.The division flourished its big guns Thursday in a live firing exercise at Camp Pickett.Artillery and armor units fired their biggest weapons including the 18-indi howitzer.Using powerful searchlights Iar.d mortar flares, Company 1, First Battalion, 103rd Armored of Johnstown conducted a concentrated training exercise last night.At Camp A. P. Hill, a flight of four jet fighter-bombers swooped in at tree-top level in a support mission on the tank-infantry training exercise.