The newest shadow war pitting western troops against Islamic radicals has begun. Except this one doesn't feature any American forces, robots or warplanes. At least, not right this second.

France has sent an as-yet-undisclosed number of troops to Mali, the beleaguered northwest African country whose northern section has been overrun by Islamist guerillas. "This operation will last as long as necessary," French President Francois Hollande announced Friday.

The goal of the campaign is to restore government control over a portion of Mali The New York Times describes as twice the size of Germany. French media reported that Malian troops re-invaded the north thanks to French military transport. It's a dramatic break from earlier French and U.S. efforts to get African forces to support a revived Malian military, apparently prompted by an Islamist campaign southward that seized the central town of Konna. And it makes Mali at least the fifth major undeclared battlefield in a global campaign between western forces and jihadi militants that stretches from Pakistan to Libya to Yemen to Somalia.

American and United Nations officials have been sounding the alarm about Mali for months. U.S. forces trained the Malian army for years – a Special Forces detachment joined in a military exercise in Mali as recently as February – but a coup in March left the U.S. legally unable to provide any additional training. Throughout 2012, the U.S. watched as al-Qaida's north African affiliate, known as al-Qaida in the Islamic Maghreb, set up training camps and provided cash and weaponry to the Islamist militia forces that came to control the north.

The U.S. military commander for Africa, Army Gen. Carter Ham, warned in December that "al-Qaida and other organizations are strengthening their hold in northern Mali." United Nations Secretary General Ban Ki-moon feared a "permanent haven for terrorists" was coalescing. "We cannot allow al-Qaida to sit in an ungoverned space and have a sanctuary and impunity," Michael Sheehan, the Defense Department's assistant secretary for special operations, told the Aspen Security Forum over the summer. "What we will do with Mali, I can't speculate, but I think you can look at the whole range of things that have been successful in partnership with (other) governments, and perhaps operating in ungoverned space."

In a November speech about the evolution of the war on terrorism, Defense Secretary Leon Panetta called the Malian safe havens an "emerging threat," raising the possibility of U.S. commando forces and drones turning their attention to yet another far-off battlefield.

France has much more familiarity. It used to be Mali's colonial overlord, and the French have a lengthy history of intervention in the region. The new Mali intervention provides something of a reversal from the past decade's worth of Western wars on terrorism, in which an aggressive America occasionally enlists reluctant support from the French. It should be noted, however, that the French played a leading diplomatic role in fanning the flames for NATO's 2011 intervention to oust Libyan dictator Moammar Gadhafi, ultimately bringing along a sometimes-reluctant President Obama.

And while France's intervention appears to be unilateral, Ham looks eager to get the U.S. Africa Command involved. The New York Times cited him saying the U.S. was exploring its options to assist the French intervention, including "repositioning satellites or sending in surveillance drones." The U.S. doesn't tend to sit shadow wars out completely.