Why Are America Forces Still in Afghanistan and Iraq?

I'm a democrat and voted for President Obama, and will again because I know He is doing a fine job. But we need to get out of Iraq and Afghanistan now. Whenever we leave, if it is a hundred years from now the out come will be the same, the enemy will take over. We must fight terrorism when ever they strike us or our friends world wide. We must fight a covert war. These wars is to costly, don't you think so?