The Iron Gates were actually a substantial length of the Danube where the river had carved its way through the tail of the Carpathians on its way to the Black Sea. Boats attempting to project control either into or out of Romania would need to navigate this section of the river. The salient features of the Iron Gates were a faster current and the surrounding high ground which would provide land based forces with the ability to interdict river movement. Trapp was anxious to close down as much of the Iron Gates as possible. While the minefields laid earlier in the week would deter the Romanians somewhat, the idea of adding another layer of protection in the form of ground forces and shore based batteries was highly attractive, especially given the dearth of indirect weaponry available in the Romanian river fleet.

The capture of the western edge of the Iron Gates was a high priority for the Austro-Hungarian forces and an entire division of the Army had been tasked with the objective. As a result, the fall of the position was never in question. Trapp's expedition was designed to disrupt the Serbian defenses and if possible capture the ground to permit the Army to quickly deploy into and control the position.

A "helpful" staff officer from Pola had sent a memo to Trapp suggesting that merely holding the western edge of the Iron Gates might not be sufficient to hold the Romanian river boats back. The solutions invented by the staff included blockships and chains. Trapp responded calmly that blockships would be devilishly difficult to place given the current and that a chain of sufficient length and heft would be difficult to secure to the relatively porous rock available on the banks. A recent review of primary sources has shown that Trapp felt that any such additional security was unwarranted. A handwritten note on the file copy of Trapp's response says, in part, "I'd like to see them try to thread that needle." The writing appears to be that of Trapp.

Counters and maps from River Fleets may be used to play Blue Danube scenarios.