The Great War

In 1918, Scapa Flow, the defeated German Navy of the German Empire accompanied by its British escorts were being escorted where they would be captured by the victorious Allied powers of the British and other powers, in our world, they were scuttled by the Imperial Navy.

...in this world, the world of Azur Lane, the defeated shipgirls were to be placed in what was effectively a "retirement home" for them, they were supposed to be demilitarized, and left to live happy lives in the territory of the Royal Navy.

This does not happen. There is no retirement home for the SMS ships.

There is only war. And this time, it is against a new enemy.

Ships of the Royal Navy and of the Ironblood were attacked by what appeared to be black ships firing beams of light, a hundred Ironblood ships of various classes, accompanied by 45 warships of the Royal Navy, fighting side by side.

It was over in an hour. The entire fleet wiped out, sinking or severely damaged to the point of being near dead.

This was the battle of Scapa Flow. The first case of the Sirens invading the world of Azur Lane.

It did not make it to the history books. Both governments covered it up. And for a time, there was peace.

World War Two. The War is in full swing, shot and shell screaming across the skies of Normandy as the Normandy landings are in full swing.

The skies blacken.
The seas roar.
Treads rattle and crush all in their way.
People die. Millions of dollars worth of damage caused.

Technology has skyrocketed. While neither side has advanced technologies in the form of jet fighters and others, rather, it comes to robotics. the emergence of the "Tactical Doll" program has bore fruit, first seeing light in the mid 20s after discovering alien technology. [This would later be censored, then covered up by Eagle Union as independent human engineering].

It is now 1945, and world war 2 does not have an end in sight, KAN-SEN versus KAN-SEN, Tactical Doll versus Tactical Doll, Man fighting Man...