Shaykh Mufid Differed With Shaykh Tusi On Jihad

I've read the biography of Shaykh Mufid by an orientalist named Tamima Bayhom-Daou, and in that it states that Shayh Mufid differed with his student on the defense of non-12er Shia rulers.

Leading HolyWar (Jihad) Muslim jurists distinguished between two kinds of jihad: jihad
for defensive purposes and jihad for the spread of Islam and its
territories.According to the Sunni jurists, the imam had a main
role in organizing wars of jihad and it was the duty of Muslims
to participate in them, regardless of whether he was sinful.
Sunnis also tended to sanction campaigns in enemy territory or
on the borders, undertaken by individuals and groups on their
own initiative and in the absence of an imam.
According to early Imamis, jihad for the spread of Islam
may only be undertaken in the presence of a legitimate imam
and under his leadership or that of his representative. Mufid,
however, held that an Imami official appointed by the illegitimate
ruler had the duty to conduct (offensive) jihad against
unbelievers, and even against some Muslim grave sinners, and
that it was the duty of his fellow Imamis to assist him. It is not
clear on what basis Mufid justified his view. It is also not clear
whether his aim was to accord legitimacy to existing practices.
Other scholars of the Buyid period did not uphold his doctrine.
Tusi, the last of those scholars, held that in the absence of the
imam, jihad against the enemies of Islam was suspended and
only defensive jihad might be carried out. According to him,
guarding the frontiers of Islam was a praiseworthy act,
irrespective of whether or not an imam was present. (There is
no evidence that he regarded the scholars as responsible for
organizing defensive jihad or calling upon the people to
wage it.) It was Tusi’s views, not Mufid’s, that influenced Imami
juristic thought on the subject for several centuries to come. (Al Mufid, Bayhom-Daou p 125-126)

 From my understanding Shaykh Mufid used the anology of Imam Ali (as) supporting the governments of the 3 calipahs. On top of that the participation of both Ammar bin Yassir (ra) and Imam Hassan (as) in the wars of the 3 calipahs is well known in history.

While Shaykh Tusi relied on narrations where Jihad is supposed to be suspended till the reappearance of the 12th imam.