Complex sentence: Unofficial military awards were fairly common in the early 20th century, however in the modern age such decorations are rare due large in part to the stringent and specific regulations regarding the issuance of military decorations and the manner of wear on military uniforms.
Split into simpler sentences: Unofficial military awards were fairly common in the early 20th century. In the modern age, however, such decorations are rare, due in large part to the stringent and specific regulations regarding the issuance of military decorations and the manner of wear on military uniforms.