[SmG Battlefire]

Then why not name it Battlefield 1918? How does what you're saying justify naming it "Battlefield 1"?

Because Battlefield 1 is like a prequel of Battlefield 4 story wise. DICE have confirmed that Battlefield 1 is related to the story of Battlefield 3 and 4.

So if I put the campaigns in chronological order, Battlefield 1, Battlefield 3, Battlefield 4.

The number at the end signifies release order, not chronological order. That's why there are movies/games ect. titled with 2 even when they are a prequel.

You are wrong because many development studios are slowly ditching the number sequences
on their franchise. That is why Call of Duty 4 Modern Warfare is the last CoD title with a number. Everything after adds sub title numbers like Modern Warfare 3 because it is part of the story or lore of Modern Warfare 2.

The only reason why Battlefield has kept its number sequence was because of the story. Having the 1 in the title makes sure that it is part of the overall lore. If I called it 1918, it would mean it has nothing to do with Battlefield 3, or 4.

Ace Combat is another great example of maintaining the numbers in their title. Ace Combat Assault horizon and Ace Combat Infinity didn't have numbers because they were the first games to take place in the real world in the franchise. But the new game Ace Combat 7 goes back to Strangereal world. Telling us that it is part of the Strangereal lore.