Balaeric Islands
The enemy forces
Mallorca defences include:
1 oversized Infantry Regiment of 7 battalions
1 artillery regiment
1 coastal artillery regiment
1 anti-aircraft group of unknown size
1 engineer group of unknown size
1 infantry battalion with bicycles
1 tank battalion (it is unclear if it actually has any tanks)
Menorca defences include:
1 infantry regiment
1 mixed artillery/anti-aircraft regiment
1 engineer group of unknown size
Ibiza defences include:
1 infantry regiment
The Spanish Air force has a smaller number of aircraft on Mallorca - nothing believed able to endanger the invasion. It is unknown if any larger ships of the Spanish navy are dedicated to the defence of the islands.
We know the Spaniards are known to be alerted. The fighting value of the Spanish troops on the Balaeric Islands are thought to be limited – old type of equipment, low morale.
Note that during the Spanish Civil war troops loyal to Franco with Italian air support managed to beat back a Republican invasion of Mallorca about 8000 troops strong.