Japanese bunkers, especially those with machine gun nests, act as mini-bosses. They are heavily armored and can suppress your advance. The best strategy is to use smoke grenades to obscure their vision, then flank and throw frag grenades inside. Alternatively, use a flamethrower to clear out the occupants if you can get close. Satchel charges are also highly effective if you can plant them. Never charge them head-on.
