They expected a fierce fight for the summit .
The Marines knew that the Japanese defenders had an extensive network of below - ground defenses , and that in spite of its isolation above ground , the volcano was still connected to Japanese defenders via the tunnel network .
defenders expected a fierce fight for the summit .
The Marines knew that the Japanese defenders had an extensive network of below - ground defenses , and that in spite of its isolation above ground , the volcano was still connected to Japanese defenders via the tunnel network .