(FILES): This July 13, 2009 file photo s

(FILES): This July 13, 2009 file photo shows a US Marine of 2nd Marine Expeditionary Brigade running to safety moments after an IED blast in Garmsir district of Helmand Province in Afghanistan. Two US Marine soldiers were killed when the explosion occured as they tried to clear a route into the Taliban heartland of southern Helmand province. The world's most powerful military machine is scrambling to fight a simple, low-tech weapon in Afghanistan that is killing and maiming American and allied soldiers at an alarming rate. The homemade bomb -- often a mixture of fertilizer, fuel and metal -- is the number one killer of NATO troops in Afghanistan and the US military has launched a massive, costly effort to try to defeat it. AFP PHOTO / Files / Manpreet ROMANA (Photo credit should read MANPREET ROMANA/AFP via Getty Images)