Complex sentence: It is uncertain which Allied unit was first to reach the Kehlsteinhaus; several claim the honor, compounded by popular confusion with the town of Berchtesgaden, which was taken on May 4 by forward elements of the 7th Infantry Regiment of the 3rd Infantry Division.
Split into simpler sentences: It is uncertain which Allied military unit was the first to reach the Kehlsteinhaus; several claim the honor. The matter is compounded by popular confusion of it and the town of Berchtesgaden taken on May 4 by forward elements of the 7th Infantry Regiment of the 3rd Infantry Division.