The history of recent foreign military interventions in Somalia is universally bad. From UN and US action in the 1990s to Ethiopia's incursion in 2006, foreign troops entering Somalia have often left behind a situation that is worse than the one they sought to improve - for their own governments and for the Somali people.
A serious threat to Kenya's national interests
This past weekend, Kenyan forces, backed with tanks and airpower, crossed into southern Somalia in pursuit of the Islamist group al Shabaab.
Insecurity in southern Somalia has allowed Somali militant groups to cross into Kenya and carry out multiple kidnappings: of tourists from beaches around Lamu, and aid workers from the world's largest refugee camp at Dadaab. Kenyans are understandably impatient for their government to take decisive action to secure their borders and security. But it is not obvious that this intervention will have the desired effect.
The extent of Kenya's ambitions is not yet clear. The intention may be to rescue those who have been kidnapped on Kenyan soil, to secure a buffer zone along the border, or even to conclusively defeat al Shabaab.
There is concern that the military intervention will worsen the humanitarian situation in Somalia. Al Shabaab has made it difficult for external NGOs to work in southern Somalia, but a full-scale war will make the region even harder to operate in.
Kenya may make impressive initial gains but the real challenge, if this incursion is meant to make al Shabaab's defeat a lasting one, will be to defeat any resulting insurgency.
Past experience warns of the unintended negative consequences resulting from such interventions. The enduring consequence of Ethiopia's intervention in 2006 was al Shabaab’s transformation from part of the Islamic Courts Union - a broad coalition - into a radical stand-alone force capable of mustering public support and controlling large areas of Somalia.
Until now, Kenya has aimed to establish a buffer zone by proxy through its support of an assortment of militias in southern Somalia. This, in addition to al Shabaab's mishandling of the famine response, has weakened the Islamist group's control in southern Somalia. However, thus far Somali militant groups have not achieved the geographic reach or the level of control that would secure the borders.
It is not yet certain that Kenya's incursion in Somalia will end badly. If Kenyan troops are engaged in only a short-term mission backed by intelligence to rescue captured hostages and provide temporary support to the TFG, and if they are able to guarantee humanitarian access before withdrawing, then the worst-case scenario may not play out. However, history has shown that in Somalia the chance of a foreign military intervention concluding successfully is, at best, limited.