The long time rule of thumb for successful peacekeeping (or Occupation & Stabilization) is that twenty troops are needed for each thousand inhabitants in the country. But this has not been the case in many recent peacekeeping operations. In Iraq there are 6 foreign troops per thousand Iraqis, and in Afghanistan there are .5 per 1,000. In African countries, peacekeeping missions have often succeeded with five or fewer troops per thousand inhabitants. What makes the difference is the quality of the troops, and the intensity and professionalism of the opposition. Despite the sensationalist headlines about the Iraqi operations, most of the country is at peace. And the foreign troops available are dealing with the remaining Iraqis loyal to the deposed government. Same thing in Afghanistan. In both cases, the resistance is from fighters who have little support of any kind. In most recent peacekeeping situations, the local armed groups were not much interested in continued fighting. That made pacification a lot easier. When there is continued resistance, it's usually better trained and equipped peacekeepers versus less capable locals. The local fighters rarely prevail.