Early Thursday morning, approximately 4,000 Marines from the 2nd Marine Expeditionary Brigade moved into the Taliban-controlled Helmand River valley in southern Afghanistan. This marked the beginning of the first large-scale operation in Afghanistan to implement a new set of counterinsurgency (COIN) practices -- practices adapted from General David Petraeus' Iraq "surge" strategy.The COIN strategy at the center of this new operation concentrates on building economic and political infrastructure, protecting the Afghan population, and establishing a working relationship between the people of Helmand and the Afghan government. Whereas the emphasis was once on "kinetic" operations targeting Taliban forces, US forces are now to be primarily concerned with assisting and protecting the Afghan people rather than hunting the enemy. In order to do this, Marine units will move into small outposts, dispersed among the population, much like they did in Baghdad during the 2007 surge.Media accounts have thus far focused mainly on the similarities between the new operation and the successful Iraq surge of 2007. However, the immense geographical and political differences between Iraq and Afghanistan will play a greater role in determining the outcome of this operation.In Iraq, concentrated counterinsurgency efforts in the central hub of Baghdad had the effect of spreading stability throughout the country. Afghanistan, on the other hand, has no such urban center where COIN efforts can be concentrated. The country's harsh mountainous landscape also serves to isolate communities from each other in a way not seen in Iraq. Less than 10 percent of the nation's population lives in large cities, and as a result stabilization efforts require greater troop numbers, more dispersed throughout the country.The enemy in Afghanistan is also quite different from that in Iraq. The Iraqi insurgency was highly fractured -- consisting of many opposing Sunni and Shiite militias and foreign terrorist elements. The US military's ability to leverage hostilities between these groups (in the form of the Anbar Awakening, where Sunni militants turned against foreign terrorist elements) was central to the success of the surge.In contrast, the Afghan Taliban has acted for some time in Helmand as a de facto government, after forcing government officials and police out of the area. This grants them a unique degree of legitimacy and support among the population not enjoyed by Iraq's militant factions. Whether Afghan citizens' support for the Taliban is merely a begrudging product of fear, or willing support, is hotly contested among experts.The US military, however, is counting on the willingness of the Afghan people to turn against the Taliban once US forces bring some degree of stability and progress. Whatever the Afghan peoples' attitudes toward the Taliban, winning their support will also require tangible improvement in the Afghan government, which is perceived as hopelessly corrupt and ineffective.The challenges presented by Afghanistan are uniquely daunting. The prospect of success will depend greatly on US forces' ability to quickly and effectively adapt strategies to unforseen circumstances and unique challenges. In a nation more populous and geographically dispersed than Iraq, and with only a fraction of the manpower, victory in Afghanistan is far from certain. In such a fight, a firm understanding of the enemy, the underlying politics, and the geography can mean the difference between victory and defeat.