Alexander the Great was antiquity\'s greatest commander

[Paralus]

Why did he "persuade" and force Greeks and Macedonians to follow him? How did he keep and increased his power after Filip died? And above all,would he be able to "persuade" or "force" greeks and macedonian to re-enforce him,had he not been as successful as he was?

Antipater had him acclaimed as king and the Macedonians present assented. From there Alexander eliminated any possible resistance. Parmenion, acquisecing in the murder of his son-in-law, brought his support and bought his positon as well as that of his adherents. That Alexander "forced the Greeks" is plain: resistance was, pardon the Borg-like tone, rendered futile.

"Forcing" the Makedones would wait until after Persia fell. From there on the anabasis is replete with grandeloquent speeches as well as more frequent coercion and bribery to convinve his Makedones to continue lovingly following him. Although it might be remembered that Amyntas had to take some young'ns east from "under the skirts" of Olympias: seems not all willingly went.

The reinforcements, early on, show many Macedonains. The rest are, usually, mercenaries, Illyrians or Thracians and such like. Mercenaries went for pay and the others had no choice.

Why didn't Hannibal secure his position back at home by force of arms or persuation if he thought that his war in Italy was the crucial thing for his country?

That begets a comparison between Carthage and Macedon. That is slippery ground. Macedonia was a monarchy and, recent arguments aside, was no "constitutional monarchy" as we would think of England or even Sparta for that matter. Alexander was working with a totally different state apparratus to Hannibal.

Alexander was a kid when he started his campaign,and if his generals and his subordinates both in the army and in Greece didn't trust,love,believe and fear him,they could have easily put someone else on his thone,of their own liking.

I doubt love had anything to do with it at the start. Fear? Absolutely. His acclamation was a fait accompli after his father's death and engineered by Antipater. Who was to gainsay it? Possible claimants were - literally - eliminated and the only other army operating was in Asia and Parmenion sold his right to choose for his security and his family's.