Meaning of “Nikaikyuu Tokushin(二階級特進)”

“Nikaikyuu Tokushin(二階級特進)” literally means a measure in the military or police to promote someone two ranks higher due to some kind of achievement.
Nikaikyuu(二階級) means two ranks, Tokushin(特進) means be specially promoted.
However, the most common situation in which this is applied is when the person has died in the line of duty.
Therefore, when the term “Nikaikyuu Tokushin(二階級特進)” appears in a drama or anime, it implicitly means that the person has died in action.
It’s a less commonly known expression compared to “Mugon no Kitaku(無言の帰宅)”, I think.

Example Conversation

A: But he got Nikaikyuu Tokushin(二階級特進), right? That’s great, isn’t it?
B: Uh… dude, that means he died…
A: Wait, seriously???

A: でも彼は二階級特進なんだろ？よかったじゃん。
B: え、おまえ、それ、亡くなったってことじゃん…
A: え、そうなの？？？