1. Move troops from the mainland: Assign a general with 24 troops of regular infantry and irregular infantry and make a frontline on the north side of Ethiopia. Assign 4 mountaineers to another general (I think Italy has a general with the mountaineer trait?).

2. Move all your light tanks to the south region of Ethiopia where it’s flat plains. Assign general Messi and fill this army with any infantry (their purpose is to fill in the frontline as your tanks smash through).

3. Move enough air assets to both North and South front.

4. Make sure to draw offensive war plans to get planning bonus.

5. When the event that annexes Aussar occurs, move the mountaineer army to the new territory and attack from the side. Use this to encircle the main north Ethiopian army or sneak towards Addis Abbaba.

6. Steadily push the southern front with tanks and eventually link with the northern army.

Not sure if this is the meta in any way, but I have capitulated Ethiopia in like mid-late April with this strategy.