In a perfect world, our friends can take care of the local jihad problem on their own.
Between perfection and worse case scenarios, there is a vast grey area where we must scale our military assistance from training and supplies and intelligence to small scale advisory and support actions. We provided such support when the Ethiopians went into Somalia a few years ago to bash the local jihadis.
And we are doing the same in Yemen:
U.S. military teams and intelligence agencies are deeply involved in secret joint operations with Yemeni troops who in the past six weeks have killed scores of people, among them six of 15 top leaders of a regional al-Qaeda affiliate, according to senior administration officials.
This doesn't mean this is the first step toward 100,000 American troops in the place. The goal is to defeat and kill jihadis. We don't need to intervene in the uprising of tribes not directly related to al Qaeda.
We had to intervene here. Hopefully, our limited involvement is also limited in time, and our assistance will be scaled back as we knock down al Qaeda strength so the Yemen authorities' capabilities compared to al Qaeda groups in Yemen is raised enough to continue the fight without our deep (but still limited) involvement.
Not that we couldnt' still face a worst case situation in Yemen. But it is too early to worry about that.