Can you help me understand this sentence please?

Question

I just came across a sentence about the National Flag of Japan. I don't think I fully understood it. So here it is:

話題の旭日旗です。長野県1滋野村2(現3ｰ東御市4、小諸市5)にあった軍6の後援7組織8「滋野軍友会」の旗9。戦前、軍関連の場合は旭日旗を使うのが常識だったのでしょう。そして旭日の光房は16あります。皇室の菊の紋章の16弁に合わせてあるのです。天皇直属の軍隊の象徴であったことを、明確に伝えています。

What I understand is this:

The topic is The Rising Sun Flag. The rising sun flag used by army support organization in the Nagano Prefecture's Shigeno Village (now Toumi and Komoro city). Before the battle and in case of the battle(軍関連の場合?), this flag was used commonly. There are 16 shining lines around the rising sun flag and the armada of Imperial Household is a gold chrysanthemum consisted of 16 petals. This chrysanthemum is in correlation with the 16 shining lines in the flag. Because this symbol symbolizes that the Emperor has a direct control over the army.

Did I understand it well?

旭日旗を使うのが常識だったの ''でしょう''

And does this phrase grammatically state a probability because of ''deshou''?

Like, Probably the flag was used commonly...

Answer 1

The word 戦前 normally refers specifically to the pre-WWII period. To say "before the battle", 戦闘前 or 戦いの前 is used.

戦前、
In the prewar period,

軍関連の場合は
if an organization was military-related,

旭日旗を使うのが常識だったのでしょう。
I suppose the use of The Rising Sun (as the flag design of the organization) was taken for granted.

Your rough understanding of the remaining sentences seems okay. (光房 seems to be a typo for 光条 or something, although its meaning is self-evident in the context.)