"The Generals," by Thomas E. Ricks PhotoQuest/Getty Images Gen. George C. Marshall, seated at center, with members of his general staff, November 1941. Gen. George C. Marshall, the United States Army's steely chief of staff during World War II, was ruthless in relieving subordinates who didn't measure up to his exacting standards. Between the time he assumed office in September 1939 and America's entry into the war on Dec. 8, 1941, he cashiered at least 600 officers - and he wasn't done yet. Numerous others, including generals, would lose their jobs when they didn't perform well enough in the caldron of combat. As the veteran military correspondent Thomas E. Ricks notes in his new book, "The Generals," "Sixteen Army division commanders were relieved for cause, out of a total of 155 officers who commanded Army divisions in combat during the war. At least five corps commanders also were relieved for cause. In the place of the duds that he cleared out, Marshall promoted promising young men like Dwight Eisenhower, a colonel until September 1941, who the following year would be named a three-star general and commander in chief of Allied forces in North Africa. That's not the way the system works today. Generals still get relieved - the fate suffered by, among others, the commander of the Walter Reed Army Medical Center and the surgeon general of the Army after a scandal was uncovered in 2007 - but usually only when their political masters intervene. Seldom are Army officers cashiered anymore by their military superiors and especially not for mere failure to perform at the highest level in wartime. Normally it takes a sexual or other scandal to bring down a senior officer. "As matters stand now," Paul Yingling, then a lieutenant colonel, wrote in a celebrated 2007 article, "a private who loses a rifle suffers far greater consequences than a general who loses a war." The flip side of the current system is that promotion even for the most successful combat leaders occurs at a glacial pace: Just as there is scant penalty for failure, there is also little short-term promise of reward for outstanding leadership. No one rockets to the top the way Eisenhower did. How did the Army change so dramatically in the past 60-plus years and what are the consequences for the future of American military power? Those are the questions that Ricks sets out to answer. Readers of his 2006 best seller on the Iraq war, "Fiasco," and of his blog, The Best Defense, know that he has strong opinions he does not try to hide. He also has a deep wellspring of knowledge about both military policy and military history. That combination of conviction and erudition allows him to deliver an entertaining and enlightening jeremiad that should - but, alas, most likely won't - cause a rethinking of existing personnel policies. Ricks spends much of his book tracing the evolution of prevailing attitudes toward the promotion and relief of generals from the 1940s to the present day. Along the way he delivers a good institutional history of the post-World War II Army, concentrating not only on failed leaders like Maxwell Taylor, one of the architects of defeat in Vietnam, and Tommy Franks, one of the architects of near defeat in Iraq, but also on generals who were more successful, like William DePuy, who helped rebuild the Army after Vietnam. One of Ricks's strengths is that his judgments are nuanced - he recognizes that while DePuy was an overly conventional and rigid division commander in Vietnam, he was a brilliant innovator in the 1970s as the first head of the Army's Training and Doctrine Command. Likewise, while crediting DePuy with helping to create the tactically proficient army that liberated Kuwait in 1991, Ricks criticizes him and his acolytes for neglecting counterinsurgency doctrine and broader issues of strategy. That second failure, he argues, helps account for the Army's inability to translate tactical success in Iraq, in both 1991 and 2003, into a lasting strategic victory. Max Boot is the Jeane J. Kirkpatrick senior fellow in national security studies at the Council on Foreign Relations and the author of the forthcoming "Invisible Armies: An Epic History of Guerrilla Warfare From Ancient Times to the Present."