Great Siege

From Tolkien Gateway
"...there's someone loose hereabouts as is more dangerous than any other damned rebel that ever walked since the bad old times, since the Great Siege."
― Gorbag

The Great Siege was a conflict, recalled by Gorbag during the War of the Ring while talking to Shagrat.[1] He was most likely referring to the Siege of Barad-dûr by the Last Alliance[2], which lasted from S.A. 3434[3] until 3441[4].