Wakanda is a closed country who does not let the world know they have highly advanced technology. In fact the world sees them as primarily a farming nation. We know they defend their borders, especially because when T'Challa goes off to try to capture Klaue, he tells W'Kabi to stay and defend the border.
How has Wakanda managed to defend it's borders for so long (e.g. against colonization by Europe and against attacks from neighboring countries) without letting others realize that their weapons (such as arm cannons and spaceships) are highly advanced? Wouldn't other countries be suspicious of a "farming nation" who nevertheless have one of the most advanced military forces in the world?