How does the Behemoth Battlefield cross the border?

Just immigrate.

First, players need to occupy another city, and then view the details of the city. There is an immigration button below the details, which displays the number of immigrants the city can accommodate. Players can immigrate with the full number of people, or manually enter the number of immigrants they want. As long as the number is within the acceptable range of the city, click Confirm to immigrate.

Immigration helps players deposit money and collect resources, and can also expand the army in the new city.