"Pakistan is a large country with various types of terrain. Some of the terrain is as bad as that in Afghanistan - much worse than in North Korea - though admitadly parts of Pakistan are flat. Also consider the length of the supply lines - much longer than those in Iraq or North Korea." All this says to me is bigger air campaign. "In any case, the Muslim world would go berserk if Pakistan was invaded causing massive problems for the U.S. the world over." Nah, Muslims are weak willed. They are historically emboldened when shown an easy hand. I think everyone in the Muslim world would probably go berserk, but for different reasons. They would cower in fear that they could be next. "In fact, the most likely scenario for such an invasion would be if a fanatical Islamist government seized power in Pakistan..." I agree completely. "Also bear in mind that after the international public relations disaster of the Iraq War, U.S. would likely have to carry out this invasion without allies." I wouldn't characterize the attention whoring of the United Nations, France, and other members of the "international community" as a disaster. I'd call it laughable. The failure to attain basing rights from Saudi Arabia, and Turkey didn't seem to matter much in the end. Pakistan borders four nations. China, India, Afghanistan, and Iran. It's safe to say we won't get basing rights from Iran, or China. We will get them in Afghanistan, and we might get them in India. Afghanistan's current government owes everything to the United States. India's will be concerned only with the effect their involvement (or non-involvement) will have on their own security. None of the issues of the Iraq war would see the light of day. Politics won't affect the logistics of this war much, aside perhaps from securing support from Britain. (The only other nation that could reasonably be expected to commit a sizable number of ground troops.) "It took 250,000 troops to invade Iraq. Somehow, I truly doubt 300,000 U.S. troops would be sufficient to invade a country much larger in size and with a population fully 6 times greater than Iraq." The 300,000 figure was based on India's involvement. "The Pakistani armed forces are also larger (610,000 men) than Iraq's and of higher quality too (and I would venture to say that Pakistani military potential in a war is significantly greater than North Korea's if you take mobilization into account). " North Korea has over a million men in their armed forces. Iraq had two million in 1991. How would they be able to mobilize while at war with the United States? Even if they could train conscripts with a fair amount of impunity, they wouldn't have enough time, or enough vehicles to make an impact. "Furthermore, unlike Iraq with the Shia and the Kurds, Pakistan does not have major ethnic groups that would be sympathetic and willing to aid or at least not oppose the U.S. invasion" Do you think it would have made any kind of a difference in Iraq if we had to fight the kurds too? "So if you combine this fact with the fact that Pakistan has 6 times Iraq's population, the obvious conclusion is that the insurgent forces would be much, much larger than in Iraq." The bulk of the Iraqi insurgents are former government officials, and foreign terrorists. The population appears to be unwilling to join with these groups against us. I don't see a nationwide anti-U.S. resistance taking place. The situation will likely be similar to Iraq, and the people, even if they are Sunnis, will be given a clear choice between the old and the new. Most people will not opt for harsh dictatorship over self-determination. Especially when restoring the harsh dictatorship involves combat against the United States army. This would make the invasion of Pakistan much more difficult and make occupation hellishly difficult