"The parallels may be most stark when it comes to the current troop increase in Iraq. Military escalation was also LBJ's answer to unrelenting attacks by the Viet Cong and the North Vietnamese in an uncontrollable civil war -- an increase from 16,800 advisers in 1963 to 545,000 combat troops by 1968. But compare that with Bush's increase of about 28,000 U.S. troops in Iraq. If more than half a million troops couldn't succeed in Vietnam, is a total U.S. force of more than 160,000 likely to pacify Iraq? And what can be done when one escalation doesn't do the trick? The more you double down, Johnson and Nixon found, the harder it is to cut your losses."