After the invasion of Iraq was completed and the regime of Saddam Hussein was toppled in May 2003, the Iraqi insurgency began. The 2003–2006 phase of the Iraqi insurgency lasted until early 2006, when it escalated from an insurgency to a civil war, which became the most violent phase of the Iraq War. Background Build up to insurgency A number of factors played into the beginning of the insurgency in Iraq. Invading U.S.-led forces were unable to immediately fill the power vacuum caused by the sudden collapse of a highly centralized state authority, resulting in weeks of virtual anarchy. Due to the fact that Saddam Hussein terrorized his military and time constraints in the planning of the invasion on the United States' side a power vacuum was created once the invasion started. This was due to the fact that Iraqi soldiers abandoned areas before U.S. forces could reach them and the fact that the United States failed to draw up plans on what to do once Saddam Hussein had been removed from power. Furthermore the rampant looting during this time period, and the inability of American-led forces to control the situation, led to Iraqi resentment. Additionally, the unexpectedly quick implosion of Saddam Hussein's regime meant that the invading forces never engaged and decisively defeated his military in any major battle; the Iraqi armed forces simply dispersed, often with their weapons, back to their homes. At least part of the reason for this, was the fact that the Iraqi military and the security services were disbanded, after the invasion by U.S.-led forces, a decision taken by the U.S. ambassador Paul Bremer. Another cause of resentment was the lack of immediate humanitarian aid and reconstruction efforts for Iraqis suffering from the invasion, the long-term effects of the repression and mismanagement of the Saddam Hussein regime, and international sanctions. A number of factions felt suspicious of long-term American intentions; the conduct of some American soldiers also served to heighten tensions. The de-Ba’athification Commission set up by the Coalition Provisional Authority, the nature of selection of the Governing Council, and other policy decisions were interpreted by Sunni Arabs as actions intended to single out their community for discrimination; this encouraged the beginnings of sectarian tensions. However, it is necessary to note, that before the invasion sectarian tensions already existed in Iraq, due to the inherent inequalities between those communities during Saddam Hussein's regime. Members