私の参謀としてついたからには、危機感を持って任にあたって貰わねば困ります。

、。

Since you've been assigned as my tactician, I'll need you to handle your duties with a proper sense of urgency — or else we'll have problems.

Literal

My strategist [as-として] attached-[since-たからには], sense-of-crisis [obj-を] having duty [to-に] [attack-obj-を] go-up-[if-not-get-ねば] troubled.

Formal/literary military-style command. ~たからには ('since you've now X / now that you've X') is a strong causal marker implying 'you've committed to X, so you have to follow through.' 参謀 ('tactician, chief of staff') is a military title. 危機感 ('sense of crisis') is a compound noun. 任にあたる ('to attend to one's duties') is a literary collocation. ~ねば is the classical/literary negative conditional ('if not'), more formal than ~なければ. 困ります ('I'll be troubled') is the polite indirect 'I can't have that happen.'