@Kaarme A fantasy world gives us a lot of leeway. The key point might not even be metal manufacturing, but rather the availability of high-purity ores and deposits. If the land was once hit by a huge iron meteor and now has huge quantities of very pure iron, that would make this possible.
Plus, even the rusting process and general chemistry doesn't have to be the same. They haven't done anything that strictly requires the same chemical elements and distributions of Earth.
In the comments last chapter someone mentioned that she is included in his harem later on, though I don't know if her family made her join, or if Balud just succeeded in making her fall for him, by accident of course.
@qwyxivi Perhaps not super strictly, but the MC has used some Earth knowledge to his benefit. It would kind of ruin the whole isekai thing if it was all useless due to the new world being so different. Though if there are lenghty stretches of barbed wire being used, then obviously you have to be correct about the iron situation in some yet to be revealed fashion.
@SapphireDemon Perhaps the author has read a bunch of (south) European novels and liked them.
bunkers and barbwire, that's great and all but without guns the bunkers are useless and the barbwire is just an obstacle. does one of the voices in MC's head know how to make guns?
@SapphireDemon From what I've seen, Mauricia is not-British-Empire, Haurelia is not-France, and Sanphan is not-Spain. Too little information to say anything about Tristovy though.
Well, the traders and travellers were stuck in a line, and in a previous chapter the nobles were making plans for blocking the only road out of the area as part of a plan to get rid of the protagonist. Could it be that the plan was put in motion and they're surprised that the road is blocked?
@doomer with the use of explosives and crossbows, barbwire funnels will still invalidate calvary and make infantry charges extremely costly. The bunkers on the other hand are still strange.