The NATO intervention in Kosovo in 1999 is being widely invoked as a precedent for military action in Syria. It is a dubious association on many levels. "Illegal, yet legitimate," was the ethically challenged verdict of the Independent International Commission on Kosovo. But unlike with Syria, NATO was claiming the right to take preventive action in its own backyard – illegal, [il]legitimate or not. And Serbia is self-evidently not Syria, most especially in terms of the spillover effect to a regional conflict.
Moreover, the efficacy of the NATO action in Kosovo has since been challenged. Hindsight has led to the realization that the aerial bombing campaign against Serbia without "boots on the ground" actually prompted Serbian President Slobodan Milosevic to abandon whatever restraint came precisely from fear of a NATO attack on the ground. In fact, violence in Kosovo intensified after the aerial strikes.
The sad truth is that post-conflict Kosovo remains, in the words of two expert observers in 2005, "a political and economic morass" with the rump Serbian population (one half of the 200,000 in 1999) living in UN-protected "isolated enclaves, fearful of reprisals by the provinces two million ethnic Albanians." And Neil Buckley wrote in May 2012 in the Financial Times that "North Kosovo remains a constant potential flashpoint – with fears that even a small spark could ignite a conflagration."