In later chapters, we find that a Zero fighter plane from either Japan's past or possibly a parallel universe version of Japan had been transported onto the world eons ago. In addition, we are introduced to Japan's version of Atlantis, the Continent of Mu, whose disappearance from the pages of Earth history are explained by it having been transported to this world 12 thousand years ago. There's also yet another empire that seems to be a parallel earth version of WWII-era Imperial Japan, with the same aggressive expansionist tendencies, so there's Modern GLORIOUS NIPPON vs WWII GLORIOUS NIPPON to look forward to in addition to modern ordinance vs Dragons in the future, I suppose.

Why do they always let themselves suffer first before taking action? Why not try to take caution or prevent an enemy attack? I knew Japan only execute self defend acts, but, c'mon, it's already in another world. After so many accidents they need to make a new policy.

When there're air battles/strikes the skies would be clear, sea battles on calm open seas, attacks would "evaporated" their targets in single shots or "broken in half" for ships (a bit beliveable early on with Japan's modern tech against mediaval - Renaissance era ships and some WW2 era tanks later, less so with WW2 era planes/cannons against magic ships that apparently can explode in single hit with normal shots and bombs), while attacks from the "less developed" sides would basically means nothing, such as wyvern's fireball directly hitting modern attack copter and both copter and pilots seems to be completely fine, or a more-or-less Victorian era artillery directly hit a WW2 "Japanese" tank and couldn't even scratch it. There is one occasion with some semblance of armies using terrain to their advantage in the "hollow moutain" that's basically a very huge and wide cave, but it's just an excuse for the story to use Japan's tank against enemy tanks without both side's planes swooping around.

The pre-curpstomp "hubris speech" also feels the same for pretty much everyone : "We are stong!" *their own armies getting blown up* "Oh no!". Seriously, I barely simplified it.

One moment that stick out to me and made me realize how shallow the author's understanding of military stuff is comes from, ironically, a submarine part, where a WW2 era sub got attack and sunk by Japan's homing torpedo.

I'm not an expert, and my "understanding "of this tech comes from the game Cold Water, but homing torpedoes have 2 stages of pings : regular "searching" pings and more rapid "homing" pings when they found and heading for their targets.

If the story had shown the sub's crews (from the country that still trying to develop working homing torpedoes but yet to have one) hearing the pings, wondering if it is trying to search for them, then realizing that it indeed does when they notice the pings get faster and closing in on them, the dread from that could easily add much more life to the story and give the readers some interesting tidbits about how homing torpedoes work. But the story only had the torpedo pinging regularly, and while the crews did shown fear, I felt much less dread reading through that part compared to a Cold Water clip of a sub trying to hide, run and dodge homing torpedoes.