With the exception of a very few large battles in Vietnam (Khe Sanh, Ia Drang), the United States has not been in a desperate fight where the outcome was in doubt since... Korea. If you recall, we damn near lost. Hackworth is one of the few talking heads who understands what heavy, sustained force-on-force infantry combat is all about, and most men I know with similar experience tend to agree with his assessments of what it takes to lead and win.
For decades, we have been in the dangerous position of having a lone USA infantry division and large number of USAF personnel standing in the DPRK's path. In 1990-91, the presence of a reinforced III Marine Expeditionary Force on Okinawa and the threat of nuclear retaliation kept Kim Il Sung at bay. But today, with far less combat power, sealift and airlift in our arsenal, Kim Jong Il might be less timid than his father if he believes we cannot fight two wars.