He launched a ground invasion of Iran without being a total failure. This was the last high-intensity conflict the world has ever seen, the Iran-Iraq war of 1980-1988.
Invading Iran from Iraq is literally a biblical curse, repeatedly. Isaiah, Jeremiah and Daniel prophesied the complete destruction of the people of Babylon at the hands of the Persians. Isaiah 13:17–18, Jeremiah 51:11, and Daniel 5. These are some of the most inhospitable mountains to launch an invasion, while the locals are known to shoot invaders with arrows (Isaiah 13:17–18 especially refers to this)
Now, in addition to this, in modern times Iran is one of the most proficient nations in the use of landmines and mortars. Landmines and mortars in mountain passes.
And Saddam leads an army through it without total defeat. Every military genius besides Rommel was insane, and Saddam is up there with the best of them.