Can the Caliphate be taken by force?

No, the Caliphate cannot be taken by force, but if it is taken by force, then the Muslims should obey that leader and give the oath of allegiance to him.

Ibn Qudamah says, “It is obligatory to obey whoever administers the caliphate, whether people agree on him and are pleased with him, or whether he captures the caliphate by conquest with the sword and is called Ameerul-Mu’mineen (Leader of the Faithful). It is forbidden to oppose and disobey him or to revolt against him and break the unity of Muslims.”[1]

 And Allah knows best.

Reference:

[1] [Radiance of Faith, p. 130]