Learn Russian: Мы должны подчиниться этому приказу.

In Russian, the verb подчиниться (to obey, to submit to) requires its object to be in the Dative case without any prepositions. You can think of it as yielding or submitting to this order.

Why does подчиниться end in -ся? Does it mean "to obey oneself"?

Not exactly. The root verb generally means to make someone subordinate or to subjugate. Adding the reflexive -ся changes it to "to make oneself subordinate" or "to submit." In English, we usually just say "to obey," but the Russian structure literally behaves like "to submit oneself to."

Why use the perfective verb подчиниться here instead of the imperfective подчиняться?

The perfective подчиниться focuses on the specific, one-time action and result of obeying this particular order. If you wanted to express a general habit or rule, like "we must always obey orders," you would use the imperfective подчиняться.

Is должны a verb? Why doesn't it have a normal verb ending?