In a dark tunnel lined with concrete‚ 60 feet below ground‚ the Israeli general held one hand above the other to illustrate his soldiers’ mission: to destroy Hamas in this sprawling city‚ and in the intricate warrens beneath it.  It’s laborious. “Underground‚ the defender has the edge. We’re working to cut it down‚” said Brig. Gen. Dan Goldfus‚ who commands the 98th Paratroopers Division of the Israeli military. He’s tasked with taking Khan Younis‚ the biggest city in the southern...