Although the armed forces intervention defied expectations of Middle Eastern militaries, the fact that officers sided with the Tunisian people actually makes perfect sense. The Tunisian military — made up of about 36,000 officers and conscripts across the army, navy, and air force — is not the oversized military common throughout the Middle East that is short on war fighting capabilities but long on prestige and maintaining domestic stability. Defense spending in Tunisia under Ben Ali was a relatively low 1.4 percent of GDP, which reflects not only the fact that the country has no external threats, but also part of a Ben Ali strategy to ensure that the armed forces could not threaten his rule. This was clearly a mistake. Had Ben Ali followed Egyptian President Hosni Mubarak, who has always taken great care to make sure that the Egyptian armed forces were well-resourced, General Ammar and his fellow officers may have thought twice about tossing their sugar daddy overboard.
Yet there is a more profound difference between the Tunisian military than its counterparts in Algeria, Egypt, and Turkey to name a few. Unlike Mustafa Kemal and his comrades, the Free Officers, and Armee Liberation National, Tunisia’s military did not found a new Tunisian regime after the country’s independence in 1956. This was largely a civilian affair under the leadership of Habib Bourgiba — a lawyer. As a result, there is no organic link between the military and the political system.
There is a real risk for the military here, however. What if the civilians cannot manage Tunisia’s new political reality? [...] If the interim government botches this very sensitive phase in Tunisia’s transition, the military may have to stay on. This does not mean that Tunisia’s officers would become directly involved in governing, but they may be forced into a tutelary role during the search for a workable political formula that will guide Tunisia going forward. Any long stay outside the barracks could have serious repercussions for the coherence and professionalism of the armed forces as the officers are exposed to the vicissitudes of politics.
I highly recommend reading the whole thing; you'll get some nice comparisons to 1952 Egypt in the bargain.