It's not brilliant, but it's certainly valid, albeit stylized, English prose. Compare the paragraph above to the following.
It was at such a midnight hour of darkness and unwonted danger that they of whom I write sprang to arms. It were as though an Hannibal were on our borders and thus viewed; it was a nobler and braver deed than that for which Leonidas and his brave followers are renowned through all historic ages. They were trained soldiers -- their trade was war -- stationed at the gateway of Thermopylae expressly for its defence, but these men, used only to the arts of peace, from the highest motives of patriotism and duty take arms and go forth into the dunnest clouds and storms of war to meet a triumphant foe and face mortal peril. Nor were inroads made upon the foe or successes attained in the East or the West till the Northern armies felt the impulse of these opportune auxiliaries and the Confederacy under their conjoined forces began to yield along the lower Mississippi and in the far away Department of the Gulf.
It was at such a midnight hour of darkness and unwonted danger that they of whom I write sprang to arms. It were as though an Hannibal were on our borders and thus viewed; it was a nobler and braver deed than that for which Leonidas and his brave followers are renowned through all historic ages. They were trained soldiers -- their trade was war -- stationed at the gateway of Thermopylae expressly for its defence, but these men, used only to the arts of peace, from the highest motives of patriotism and duty take arms and go forth into the dunnest clouds and storms of war to meet a triumphant foe and face mortal peril. Nor were inroads made upon the foe or successes attained in the East or the West till the Northern armies felt the impulse of these opportune auxiliaries and the Confederacy under their conjoined forces began to yield along the lower Mississippi and in the far away Department of the Gulf.