Locke & Widmore face off at the sonic fence on Hydra Island

Locke reaches Hydra Island alone in a canoe and immediately sees the portable sonic fence set up all the way down the beach. Seamus and other armed members of Widmore's group take shots and Locke and tell him not to move. Locke says that he comes in peace.

They walk up the beach towards the Ajira plane with Locke staying on the ocean side of the fence. Charles Widmore emerges and Locke knows who he is. Widmore reveals that he knows that Locke is obviously not really Locke. He says other than that, all he knows is "myth, ghost stories, and jungle noises." Locke points out that Widmore knows more that he's letting on since he knew to put up the sonic fence pylons.

Widmore denies that he took Jin, causing Locke to repeat Widmore's words from season 5. Locke says "A wise man once said that war was coming to this island, I think it just got here."

So how much does Widmore actually know about the black smoke/Man in Black/Locke? Clearly he knows more than he's letting on, but how much is that? Something tells me this war is going to have a few casualties.