Complex sentence: Later, it became fashionable for tunics to be produced with sleeves and worn with braccae, especially in relatively cold northern territories such as Britain and Germany where similar clothes were already in existence among the native populations.
Split into simpler sentences: Later, it became fashionable for tunics to be produced with sleeves and worn with braccae. This was especially the case in relatively cold northern territories such as Britain and Germany where similar clothes were already in existence among the native populations.