Fighting during the sacred months

Allaah says (interpretation of the meaning):

“They ask you concerning fighting in the sacred months. Say: fighting therein is a great (transgression)…” [al-Baqarah 2:217]

The majority of scholars state that (the prohibition of) fighting in the sacred months is abrogated by the aayah (interpretation of the meaning):

“Then when the sacred months have passed, then kill the Mushrikeen wherever you find them…” [al-Tawbah 9:5] , and other aayat and reports which are general in application and which include commands to fight them.
Others say: it is not permissible to initiate fighting during the sacred months, but it is permissible to continue and conclude fighting, if it started at a different time. The fighting of the Prophet (peace and blessings of Allaah be upon him) against the people of al-Taa’if is interpreted in this way, because the fighting had begun at Hunayn in Shawwaal.

The above does not apply to fighting in self-defence. If the enemy attacks the Muslim lands, it is obligatory for the inhabitants to defend themselves, whether that happens during a sacred month or not.