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Of all the ethnic groups they could pick out in Iran to do a landing and expect support from, the Balouchis are the most likely. Kurds are not in a geographic position where an invasion is plausible and Iranian Azeris would rather annex Azerbaijan then join them as separatists. Turkmen and loor and too small of a group, nomadic, and share a very small border with a country that's explicitly neutral in all its affairs (Turkmenistan) or actively hostile to the US (Afghanistan).

Balouchis share a border with Pakistan, where separatists often agotate from. They are Sunni, extremely poor by the standards of the rest of Iran, and due to foreign interference a growing sentiment of Wahabbism has taken hold of parts of the community. Sistan-Balouchistan is largely rural and under developed outside the major cities and ports. However, I wouldn't say that insurrectionist sentiments are very prominent, especially after the US-Israel's aggression.

I would expect that quite a few Balouchis have become Basijis in preparation to an invasion, and although the land is less mountainous then the Western parts of the country, it's still not entirely flat.