ただちに行動を起こさなければならない。

at once; immediately; directly; in person; automatically

action; conduct; behaviour; behavior; mobilization; mobilisation

indicates direct object of action; indicates subject of causative expression; indicates an area traversed; indicates time (period) over which action takes place; indicates point of departure or separation of action; indicates object of desire, like, hate, etc.

to raise; to raise up; to set up; to pick up; to wake; to wake up; to waken; to awaken; to cause; to bring about; to lead to; to trigger; to give rise to; to create; to generate (e.g. heat, electricity); to produce; to start; to begin; to launch; to establish; to found; to set up; to open; to plough; to plow; to till; to fall ill with; to transcribe; to write down (what is spoken); to turn over (a card)