The first thing I saw last month when I walked into the belly of the dark grey C-17 Air Force cargo plane was a void - something was missing. A missing left arm, to be exact, severed at the shoulder, temporarily patched and held together. Thick, pale flesh, flecked with bright red at the edges. It looked like meat sliced open. The face and what remained of the rest of the man were obscured by blankets, an American flag quilt, and a jumble of tubes and tape, wires, drip bags, and medical monitors.

That man and two other critically wounded soldiers - one with two stumps where legs had been, the other missing a leg below the thigh - were intubated, unconscious, and lying on stretchers hooked to the walls of the plane that had just landed at Ramstein Air Base in Germany. A tattoo on the soldier's remaining arm read, "DEATH BEFORE DISHONOR."

I asked a member of the Air Force medical team about the casualties they see like these. Many, as with this flight, were coming from Afghanistan, he told me. "A lot from the Horn of Africa," he added. "You don't really hear about that in the media."

"Where in Africa?" I asked. He said he didn't know exactly, but generally from the Horn, often with critical injuries. "A lot out of Djibouti," he added, referring to Camp Lemonnier, the main US military base in Africa, but from "elsewhere" in the region, too.

Since the "Black Hawk Down" deaths in Somalia almost 20 years ago, we've heard little, if anything, about American military casualties in Africa (other than a strange report last week about three special operations commandos killed, along with three women identified by US military sources as "Moroccan prostitutes", in a mysterious car accident in Mali). The growing number of patients arriving at Ramstein from Africa pulls back a curtain on a significant transformation in 21st century US military strategy.

These casualties are likely to be the vanguard of growing numbers of wounded troops coming from places far removed from Afghanistan or Iraq. They reflect the increased use of relatively small bases like Camp Lemonnier, which military planners see as a model for future US bases "scattered", as one academic explains, "across regions in which the United States has previously not maintained a military presence".

Disappearing are the days when Ramstein was the signature US base, an American-town-sized behemoth filled with thousands or tens of thousands of Americans, PXs, Pizza Huts, and other amenities of home. But don't for a second think that the Pentagon is packing up, downsizing its global mission, and heading home. In fact, based on developments in recent years, the opposite may be true. While the collection of Cold War-era giant bases around the world is shrinking, the global infrastructure of bases overseas has exploded in size and scope.

Unknown to most Americans, Washington's garrisoning of the planet is on the rise, thanks to a new generation of bases the military calls "lily pads" (as in a frog jumping across a pond toward its prey). These are small, secretive, inaccessible facilities with limited numbers of troops, spartan amenities, and prepositioned weaponry and supplies.

Around the world, from Djibouti to the jungles of Honduras, the deserts of Mauritania to Australia's tiny Cocos Islands, the Pentagon has been pursuing as many lily pads as it can, in as many countries as it can, as fast as it can. Although statistics are hard to assemble, given the often-secretive nature of such bases, the Pentagon has probably built upwards of 50 lily pads and other small bases since around 2000, while exploring the construction of dozens more.

As Mark Gillem, author of America Town: Building the Outposts of Empire, explains, "avoidance" of local populations, publicity, and potential opposition is the new aim. "To project its power," he says, the United States wants "secluded and self-contained outposts strategically located" around the world. According to some of the strategy's strongest proponents at the American Enterprise Institute, the goal should be "to create a worldwide network of frontier forts", with the US military "the 'global cavalry' of the twenty-first century".