They are figting harder because they know they are losing.

At Pen and Sword:
"For a long time, I dismissed much of the administration's self contradictory rhetoric as garden-variety political blather. But I started getting worried back in summer of 2005 when young Mister Bush said of the terrorists, "I think they're losing. That's why they're still fighting."

"That's when it hit me. This "still fighting because they're losing" business wasn't just some misstatement that belly-flopped its way off the end of Mister Bush's tongue. It was a carefully crafted talking point invented at a conservative think tank and blessed by Karl Rove for distribution to the administration's anointed echo chamberlains. "

"And I realized that the core essence of the neoconservative cabal is out-and-out March Hare madness. "