having failed in his attempts to penetrate the port arthur fortifications by direct assault, nogi now ordered sappers to construct trenches and tunnels under the russian forts in order to explode mines to bring down the walls. by now, nogi had also been reinforced by additional artillery and 16,000 more troops from japan, which partially compensated for the casualties sustained in his first assaults. however, the major new development was the arrival of the first battery of huge siege howitzers, replacing those lost when the transport "hitachi maru", loaded with a battalion of the first reserve regiment of the guards, was sunk by russian cruisers on june 15, 1904. the massive 11-inch howitzers could throw a 227-kilogram (500.4-pound) shell over 9 kilometers (5.6 miles), and nogi at last had the firepower necessary to make a serious attempt against the russian fortifications. the huge shells were nicknamed "roaring trains" by the russian troops (for the sound they made just before impact), and during their period at port arthur over 35,000 of these shells were fired. the armstrong howitzers had originally been installed in shore batteries in forts overlooking tokyo bay and osaka bay, and had been intended for anti-ship operations.