NOVA Secret Tunnel Warefare airs January 6, 2016 on WSKG-TV. 100 years ago in the winter of 1916, Allied forces devised a plan to break the World War I trench warfare stalemate: one million pounds of explosives hidden in secret tunnels under the German lines. On June 7, the explosives were simultaneously triggered at the Battle of Messines in Belgium – probably the single biggest non-nuclear explosion of all time, heard clearly 150 miles away in London. 10,000 Germans were killed instantly. Now, archaeologists are revealing the extraordinary scale and risks of the Allied tunneling operations in the biggest excavation ever undertaken on the Western Front. NOVA follows bomb disposal experts as they clear topsoil packed with shrapnel and unexploded shells and probe one tunnel system connected to what is probably the world’s largest unexploded bomb – a mine consisting of 22 tons of explosives that was discovered and flooded by German engineers before the attack.