The US military left Iraq in December with new technologies that are likely to change the shape of future wars. But some of the skills developed alongside are in danger of falling away, several people throughout the ranks worry.
Ten years ago, the US military was firmly under the control of the generals. It was steeply hierarchical, slow to evolve and squarely focused on "big wars" between armies of opposing nations.
A decade of painstaking, often painful lessons resulted in a military that is in many ways fleeter and more adaptable. It is also flatter: The generals are still in charge, but Iraq and Afghanistan showed that independent thinking by low-level captains and lieutenants is also critical to success.
In any inventory of changes, the most obvious may be equipment. To protect soldiers from roadside bombs, the Pentagon built $45 billion worth of mine-resistant, armor-protected vehicles, the V-hulled trucks known as MRAPs. Military officials say MRAPs have saved hundreds of lives, though the hulking vehicles' utility remains unclear for future arenas.
The Pentagon also built sophisticated jammers to foil radio-detonated roadside bombs, which are likely to become standard issue against improvised explosive devices (IEDs), the probable weapon of choice in future land wars. The unmanned drones it acquired to battle insurgents have transformed how the US fights wars and now are used extensively by the CIA.
But the two wars also helped push the military strategy from a playbook of offense and defense to one that includes a third class of operations -- strategies that include counterterrorism and counterinsurgency, aimed at maintaining stability for populations in often-hostile zones and turning potential allies into enemies.
Stability operations are not popular in parts of the White House. Some administration officials see them as overly costly missions that threaten to tie down the US military in long-term occupations that do little to improve American security.
Such hostility in some quarters has caused some officers to fear that some of the counterinsurgency skills honed in Iraq will be lost -- including running detainee operations, conducting interrogations and collecting intelligence with aerial drones, areas of high expertise that support efforts to cripple insurgent networks and head off spectacular attacks.
Others worry that the skills learned through hard years of fighting -- how to react quickly to ambushes and spot IEDs before they explode -- will fade. The military remade its training centers to teach such skills, but instilling the knowledge into the next generation of soldiers will require retaining senior non-commissioned officers who spent the most time hunting insurgents in Iraq.
Read more: Wall Street Journal