Ruse, n.
Etymology: [F., fr. OF. reüser, rehuser, to turn aside, to shuffle, retreat, fr. L. recusare to refuse; pref. re- again + causa cause. See Cause, and cf. Recusant.]
An artifice; trick; stratagem; wile; fraund; deceit. Ruse de guerre ( Etym: [F.], a stratagem of war.
Shades of meaning
Fernald has no entry of its own for ruse; he lists it under artifice, pretense.
Where he writes about it:
A ruse or a blind may be quite innocent and harmless. — from artifice
A ruse is something (especially something slight or petty) employed to blind or deceive so as to mask an ulterior design, and enable a person to gain some end that he would not be allowed to approach directly. — from pretense