Easygoing Territory Defense by the Optimistic Lord: Production Magic Turns a Nameless Village into the Strongest Fortified City (Light Novel) Vol. 4

Van and Arte have little time to enjoy their hard-won peace, as the war with Yelenetta continues and the king calls on Van's genius yet again. Ordered to build temporary fortifications for an army on the move, Van ends up constructing an entire fortress in the middle of the battlefield! But his exploits are making him enemies among the other nobles, who begin to plot against him. Will their jealousy be Van's downfall--or will his newly constructed base hold strong?