Why hold'claim Osgiliath?

[Nerwen]

You can tell Cody he was on the right track.

Osgiliath had strategic value. It was the easiest place to cross the River Anduin, which Sauron's army had to do in order to attack Gondor.

"And the Enemy must pay dearly for the crossing of the River. That he cannot do, in force to assail the City, either north of Cair Andros because of the marshes, or southwards towards Lebennin because of the breadth of the River, that needs many boats. It is at Osgiliath that he will put his weight, as before when Boromir denied him passage."

–Denethor in "The Siege of Gondor" (The Return of the King.)

That answer your question?

While I'm here– welcome back to the Downs. That's a rather cool signature you've got there.