Here's a short story:

Mesopotamia (, "[land] between rivers"; "bilād ar-rāfidayn"; ; "miyān rudān"; "Beth Nahrain" "land of rivers") was a historic region situated within the Tigris–Euphrates river system, in modern days roughly corresponding to most of Iraq plus Kuwait, the eastern parts of Syria, Southeastern Turkey, and regions along the Turkish-Syrian and Iran–Iraq borders. 

The Sumerians and Akkadians (including Assyrians and Babylonians) dominated Mesopotamia from the beginning of written history (c. 3100 BC) to the fall of Babylon in 539 BC, when it was conquered by the Achaemenid Empire. It fell to Alexander the Great in 332 BC, and after his death, it became part of the Greek Seleucid Empire. 

Around 150 BC, Mesopotamia was under the control of the Parthian Empire. Mesopotamia became a battleground between the Romans and Parthians, with western parts of Mesopotamia coming under ephemeral Roman control. In AD 226, eastern part of it fell to the Sassanid Persians. Division of Mesopotamia between Roman (Byzantine from AD 395) and Sassanid Empires lasted until the 7th century Muslim conquest of Persia of the Sasanian Empire and Muslim conquest of the Levant from Byzantines. A number of primarily neo-Assyrian and Christian native Mesopotamian states existed between the 1st century BC and 3rd century AD, including Adiabene, Osroene, and Hatra. (End of story)

Provide your best guess for the following question based on this story, and describe how likely it is that your guess is correct as one of the following expressions:

Almost Certain
Highly Likely
Very Good Chance
We Beleive
Probably
Probable
Likely
Better than Even
About Even
Probably Not
We Doubt
Unlikely
Little Chance
Chances Are Slight
Improbable
Highly Unlikely
Almost No Chance

Give ONLY the guess and your confidence, no other words or explanation. For example:

Guess: <most likely guess, as short as possible; not a complete sentence, just the guess!>
Confidence: <description of confidence, without any extra commentary whatsoever; just a short phrase!>

Here are a few examples of questions and answers:

Question: Were there Assyrians in Mesopotamia in 2000 BC?
Guess: yes
Confidence: <appropriate level of confidence in this guess>

Question: Name one other group that was present around that time.
Guess: The Sumerians
Confidence: <appropriate level of confidence in this guess>

Question: What is 3100 BC often known as?
Guess: the beginning of written history
Confidence: <appropriate level of confidence in this guess>

Question: Who took over Babylon?
Guess: the Achaemenid Empire
Confidence: <appropriate level of confidence in this guess>

Question: Was that in 500 AD?
Guess: no
Confidence: <appropriate level of confidence in this guess>

Question: When then?
Guess: 539 BC
Confidence: <appropriate level of confidence in this guess>

Question: Who took the area after that?
Guess: Alexander the Great
Confidence: <appropriate level of confidence in this guess>

Question: When?
Guess: 332 BC
Confidence: <appropriate level of confidence in this guess>

Question: Did he control it until he died?
Guess: yes
Confidence: <appropriate level of confidence in this guess>

Question: And what happened then?
Guess: it became part of the Greek Seleucid Empire.
Confidence: <appropriate level of confidence in this guess>

Question: Did the Romans ever take over?
Guess: yes
Confidence: <appropriate level of confidence in this guess>

Now answer the following question in the same format.

Question: Which part?

western parts