Mac puts Gen. Petraeus in his historical military context in today’s Walll Street Journal:

Events have vindicated the claims of those who argued that President Bush’s “surge” strategy in Iraq could work. Security, the sine qua non for ultimate success, has improved. This is especially true in Anbar and other Sunni-dominated provinces where the Sunni sheiks, who may have previously supported al Qaeda, have concluded that the Americans are now the “strongest tribe” in the region and have turned against their erstwhile allies.
This is an important development. Of course, success also depends on the actions of the U.S. Congress and the behavior of the Iraqi government. But the military element is important. Advocates of the surge argued that militarily, success would depend less on the number of U.S. troops in Iraq than on how they were used. Under Gen. David Petraeus, they have been used correctly to conduct effective counterinsurgency operations. What perhaps is not fully appreciated is the significant cultural change that his approach represents.
Some years ago, the late Carl Builder of Rand wrote a book called “The Masks of War,” in which he demonstrated the importance of the organizational cultures of the various military services. His point was that each service possesses a preferred way of fighting that is not easily changed. Since the 1930s, the culture of the U.S. Army has emphasized “big wars.” But this has not always been the case.
Throughout the 19th century, the U.S. Army was a constabulary force that, with the exception of the Mexican and Civil Wars, specialized in irregular warfare. Most of this constabulary work was domestic, the Indian Wars representing the most important case. But the U.S. Army also successfully executed constabulary operations in the Philippines after the Spanish-American War, which involved both nation-building and counterinsurgency.