The medieval Lithuanian shield reconstruction, Ryn Castle, Poland. The coat of arms of the Grand Master of the Teutonic Order is on the shield not by mistake. Because of the design with the convex semicylinder shape in the middle lengthwise, the Lithuanian shield was very effective in deflecting sword blows during fighting. The successful design was not left unnoticed by the sworn enemy of the Lithuanians – the Teutonic Knights. They adopted this weapon and subsequently used it in warfare against the Grand Duchy of Lithuania