amphibia amphibious armor armored personnel armour battle Camouflage car carrier gun history military Poland shield swim tank cannon vehicle war weapon OT-64 armoured caterpillar cog complex England heavy machine mesh metal old part personnel tank track wheel BRDM soviet tracked access-denied advice alert appropriate-behavior appropriate-behaviour authorised-approval authorized-approval behave behavior behaviour communicate communication denied direction entry-denied entry-prohibited exception keep-out limitations limited no-access no-entry not-allowed not-permitted permission-denied prohibited prohibition restricted restriction restrictions sign staff staff-approval staff-approved unauthorised unauthorized warning authorised danger risk army bomb explode explosive fuse grenade power