What are some places other than Gaul that Julius Ceasar could have conquered and used as a platform to take control of Rome? What would the effects of an alternate conquest be?
Dacia was an option, particularly since he originally was intended to have Illyria as his province.
Dacia may have been a tougher nut to crack, however. Less divided, more defensible... but also richer.
Dacia richer than Gaul?
Maybe Germania? Or do a Pompey and go East.
Had he not be killed on the Ides of March, he planned on going back to conquer Britain and then invade Persia.
Any chance of him trying his luck in North Africa outside of Egypt (or going into Egypt earlier, for that matter)?
I don't think he would have ever been able to fully bring the Amazigh to heel, so he might not be remembered as a great conqueror even if he does take over Rome in that scenario.
And then he dies and the Empire splits into pieces.OK, let's consider this scenario; presuming that Julius Caesar is not killed in the first skirmish by a stray dart, and has approximately the same amount of luck as in OTL.
So, in ATL he gets North Africa instead of Gaul.
Contrary to popular belief the unconquered Berber polities were not poor, they were moderately wealthy and so they might saturate the initial greed of his legions and Caesar might get something left to buy him support in Rome.
But the real treasure of the North Africa is Berber cavalry, which was a cornerstone of the Hannibal's glorious victories; Scipio used the Berber horse against Hannibal with crushing effect.
If those two venerable men saw the advantages of using the Berber cavalry, I am pretty sure Caesar would use them too. They would make his personal guard (as the Germans in OTL), and he would gather 20 000 of them under his command... What for?
- For Egypt of course!
Egypt stinking rich close by is too much of temptation to resist. The Berbers might start the invasion by land, they can do that, I assure you, they did it in the Middle Ages.
The proper Roman Army would be transported by sea, traditionally, by fleet.
Cause for war? Julius Caesar did not care too much about it in Gaul, he would find something.
But after initial success and tremendous treasure the bribes would flow to Rome to get him all support he needs.
Actually Egypt is much easier to pacify than the Gauls who never knew how to live under foreign occupation.
So after quelling some revolts in Egypt and North Africa, Julius Caesar is moving east, to Syria, now followed by 30 000 Berber cavalry (those guys are better kept close by, and they are damn good).
In the East Caesar finds some ways to extort some money from the Roman allies, provoke some rebellions and get even more money suppressing them, installing order.
The rich Arab trade cities are conquered with a lightning speed by his Berbers who are not afraid of the desert raids.
So he has all means to install sufficient garrisons in the newly conquered provinces and gather a great army... well, you already guess - for the war against Parthia.
Having 30 000 Berber cavalry Caesar is not going to be annihilated by the Parthian horse. A few brilliant battles, sieges and Mesopotamia is a part of the Roman Empire and Caesar is the richest man in Rome.
But something is missing yet... yes, Alexander the Great's glory.
So Caesar is gathering all the Berbers he could get; actually by that time they are flocking to him attracted by his luck and generosity.
He creates four legions using the Greeks and Macedonians (but the centurions are the Romans of course with some cohorts of 'ethnic' Romans in every 'Greek legion'). The Greeks owned the East just a few years ago, they still remember it.
The Berbers are commanded by the Roman officers, and the Roman citizenship is poured on these brave and skilled horsemen.
So, this is not a Greeko-Berber army, that's the Roman army which is repeating the campaign of Alexander the Great. By moving Caesar actually restoring the Seleucid power structures, only with the Romans at high military and administrative positions. Like Alexander the Great Caesar settles his soldiers as permanent garrisons on the conquered lands; but unlike Alexander he doesn't need to found cities as there are already plenty of them. The settlers are richly awarded by lands and cash, the Hellenes expected that and don't mind too much. Some Berbers are outraged by staying forever so far from home and revolt; well the still have to stay, dead and buried for defiance to Julius Caesar.
So 40 000 Berbers are settled to the East of Mesopotamia constituting the backbone of the Roman power there and depriving North Africa of any means to rebel.
So most of the Eastern part of the Alexander the Great Empire is restored with the exception of Indian parts. Caesar crossed the Indus, burned some cities and came back.
Leaving a few Roman legions in the strategic places he is returning to Rome, where even his sworn enemies admit that he is the greatest Roman who ever walked this Earth.
It's 50 BC, time to start Civil War...