It’s only recently that Orthodoxy was acknolwedged as a distinct Christian faith for military purposes. How many forms filled out even today allow only “Catholic,” “Protestant,” “Jewish”, and “Other”, with no space to write an alternative?
When my Orthodox father was in WW2, your dog tag said, P, C, or J. Everybody else, such as he, was an X.
The same story was told by a well respected Orthodox metropolitan about his experience as a Marine–and that was in the '60’s.
As it turns out, most Orthodox chaplains are priests of the OCA. They function as priests of the diocese wheresoever the base is located.
There’s a big practical problem, too. My understanding is that base chapels allow only 50 min for services, and Orthodox services take considerably longer.
The actual number of Orthodox is estimated at 2-6 million.