This is exactly what the Muslims want. This is why Muhammad waged war by terrorism and so have his followers through the centuries. To use terror to rattle and depress enemies with the objective being to get their adversaries to surrender and retreat. This lessens Muslim casualties and leads to easier conquest
Israeli soldiers have also been mutilated this way in wars they fought with Egypt, Syria etc.
Terror is the way Mohamed made war and most Muslims have emulated him ever since.
From the effing Koran:
008.012 I will cast terror into the hearts of those who disbelieve. Therefore strike off their heads and strike off every fingertip of them.
From Hadiths:
Allah's Apostle said:
"I have been made victorious with terror" Bukhari 4:52:220
Yes, the Muslims have succeeded in shaking us up. But don't think for even a minute that this won't make our service men and women even more determined to destroy this enemy. Ultimately, I think this will have the opposite effect than what the Muslims hoped for.