Obama announced a new strategy for Afghanistan

dec. 12th, Obama has announced a new strategy. it is for Afghan and he said that US will send US military more 30000 by early next year. however, he also said that the troop will start to transfer from Afghan by July 2011.
he aims that US want Afghan to become control their county by themselves. it means that US government think that Afghan should keep peace and they have to run their county without US power.
i think that it can hear very good for Afghan what US said, but i dont know why US need to increase the troops more 30000??? what the troops for? they are going to need shoot somebody? it is very strange for me. of cause, i know the situation in Afghan is really terrible now, so US need to protect themselves. however, i dont think US force Afghan to keep safe by US. i mean that Afghan can become to get the peace by themselves, because any countries can get peace themselves. and moreover, every countries have rights. so i think the US privent the Afghans peace....