Adm. Henry's flagship is the USS Iowa (BB62), lead ship of the Iowa class, which is seen earlier in this episode. However, as Byron approaches on the Admiral's barge, we see it approaching the BB60, the USS Alabama, a ship of the South Dakota class.
Related to the rank change for Von Roon, the rank Brigadier General did not exist in the German Army. The first general rank was major general, followed by: General of Infantry (or other branch), Lieutenant General, Colonel General and Field Marshal. The rank of Brigade Leader (Brigadefuehrer) did exist in the SS.
USS Barracuda, SS163, was not stationed in the Pacific Ocean in September 1944. From September 1942 onward she was stationed in the Mexican gulf and the Atlantic after being converted to a cargo submarine.
When Byron Henry steps aboard the USS Iowa, the admiral orders to write him down as commander of the SS204 USS barracuda. Wrong the SS204 was registered under the name USS Mackerel, lead ship of the Mackerel Class submarines.
Late into the mini-series, both Byron and his father Victor can be seen wearing the Navy Achievement Medal. This decoration did not exist during World War II, with the first awards of the medal made in 1961.