Original: Shalmaneser regarded it as so menacing to Assyria's interest that he undertook an expedition in 857, claimed to have destroyed the capital Arzashkun The Ancient Assyrians - Page 12 by Mark Healy, penetrated as far as Lake Van, and left his inscription on Mount Irritia.
Simplified: Shalmaneser regarded it as so important to Assyria's interest that he started an mission in 857, and said that he destroyed the capital Arzashkun, located as far as Lake Van, and left his inscription on Mount Irritia.