Let me a tell you a little story that I hope you will take to heart. It is about an American President who sent young Americans to die in a war conducted against a foreign country that had done nothing to threaten the security of Americans in their own land. The war was not popular and was dragging on far longer than most people who voted for this President ever expected. It went on even longer than World War II, for that matter. The problem wasn't necessarily that the United States could not beat back the official army of the foreign country. The real enemy was the insurgency within the foreign country.
These insurgents were not particularly happy with their own government, but their real target was the American soldiers who they felt had invaded their land for less than noble purposes. Far more knowledgeable about the geographical landscape of the country, as well as the political and cultural landscape, these insurgents proved quite adept at using the weaponry of the Americans against themselves. They were able with startling ease to procure American weapons and actually preferred to use these weapons because it was so easy to get proper ammunition for them. They increased their numbers by recruiting like-minded people and this was made all the easier by the political blindness of the Americans conducting the war in Washington, D.C. Their country had been no utopia prior to the war, but the invasion by foreign troops had made life significantly worse for most citizens.
The insurgents were highly organized in their recruiting and training techniques, turning even people who had not been extremists before into hardcore true believers. They used their stolen weapons and ammunition effectively against the American troops who also had the disadvantage of not receiving the highest quality protective equipment. Because the insurgents didn't have to deal with stupidly instituted military chains of command and other bureaucratic and political obstacles to progress they could strike much more quickly and then disappear. These insurgents also engaged in violent acts of terrorism, including kidnapping and even political assassinations. Neither the military nor the political tacticians back home had the slightest idea how to combat the insurgents but nonetheless continued to report that their war was going well and all that was really required to achieve ultimate victory was patience. It takes time to win a war against an invisible enemy, but the American military might could not be overcome.