Psychology and perception play a role, but mass warfare is a battle of logistics.
We can win every battle in Iraq, as we did in Viet Nam, and still lose the war at home, which is all that counts.
I remember it well. I was in Vietnam during the Tet offensive in 1968. Vietnam was the first televised war, which is why public opinion played such a role. WWII and Korea were not brought into the living rooms every night nor were the MSM hell bent on seeing the US lose.
I daresay when a conflict is between a great power and a limited insurgency, logistics are a minimal concern. The Viet Cong got by on almost nothing and won, and the jihadis are fighting the U.S. with leftover explosives and suiciders. As long as more and more are willing to die for Allah, they cannot be stopped.
Perception is ALL in this war. Television rules the world. As long as teevee lefties work to end this war by filtering the truth, the jihadis will win. It's inevitable.