According to a graph by U.S. State Department, terrorist attacks escalated worldwide following the United States' 2001 invasion of Afghanistan and 2003 invasion of Iraq. Dame Eliza Manningham Buller, the former head of MI5, told the Iraq inquiry, the security services warned Tony Blair launching the War on Terror would increase the threat of terrorism. Robert Pape has argued that at least terrorists utilizing suicide attacks—a particularly effective form of terrorist attack—are driven not by Islamism but by "a clear strategic objective: to compel modern democracies to withdraw military forces from the territory that the terrorists view as their homeland". However, Martin Kramer, who debated Pape on origins of suicide bombing, stated that the motivation for suicide attacks is not just strategic logic but also an interpretation of Islam to provide a moral logic. For example, Hezbollah initiated suicide bombings after a complex reworking of the concept of martyrdom. Kramer explains that the Israeli occupation of the South Lebanon Security Zone raised the temperature necessary for this reinterpretation of Islam, but occupation alone would not have been sufficient for suicide terrorism. "The only way to apply a brake to suicide terrorism," Kramer argues, "is to undermine its moral logic, by encouraging Muslims to see its incompatibility with their own values."