Objectives must be activated. Directives are activated separately.
The chain of events is most commonly that an objective for the Force gets activated first but that is not necessarily the case. You could issue directives to your Formations (Attack [A] for instance). The Formation would not have any target however, so until the Force objective activated... it would have to wait. Most typically Force objectives are issued and activated first, then Formation directives are issued and activated.
Something else to be aware of is that if there is no Army Commander present, the Force Commander can set his own Force objective via a Leader Action. This would speed up the course of events some. This can still be done if an Army Commander is present, but there is a penalty modifier.