Complex sentence: The fortification was used as a military training base through the second world war under he name Camp Niagara however the grounds were eventually abandoned by the military in 1965 and is now a National Historic Site, maintained by Parks Canada.
Split into simpler sentences: The fortification was used as a military training base through the second world war under the name Camp Niagara. The grounds were eventually abandoned by the military in 1965 and are now a National Historic Site, maintained by Parks Canada.