http://www.militaryinfo.com/news_story.cfm?textnewsid=75 and http://www.episcopalchurch.org/79901_89904_ENG_HTM.htm
are both worth reading. Prior to THIS CHAPEL they conducted any services in conference rooms, etc. Otherwise there were only small “prayer rooms”. So the chapel you know of is described as the first chapel.
"This is the first large chapel at the Pentagon," Benson said. " It is the first time we've had a place large enough to conduct services, which will include Jewish, Christian and Islamic."
Not the first chapel, the first large chapel.
Believe what you want. I all but lived in the building during my time there. I got direct confirmation today via email from someone who has worked there off and on since the early 70's (and continuously since 1992). You can let a couple of throwaway lines in internet news stories be the foundation of your grand stand if you like.
The bottom line is that this story is nothing but leftist agitprop…like I said very early in this thread...before you decided it was more important to dig into minutiae.