I was wondering how did Numenorians managed to defeat Sauron after the fall of Eregion? And what did Sauron do all those years between his defeat and Fall of Numenor? How did he managed to survive the downfall of Numenor and managed to get a physical form during the War of the Last Alliance? Was he so afraid to meet Numenorians in the field that he waited all the time and lured them into the trap of getting him prisoner so he could poison the Numenor from within? But I think the Numenor was already poisoned with anti-elven and anti-valar ideas before Sauron was taken captive.

You sound as if you're having fun with your Second Age project

A brief answer to your question: There were multiple reasons, but Númenórean sea power ranked near the top of the list. The Númenóreans flanked Sauron's armies in Eregion by landing at the mouthes of several of the rivers, most notably the Gwathló. The Dark Lord only escaped to Mordor with a handful of survivors, & it took him many years to regain his strength.

The Númenóreans meanwhile continued to explore & colonize the coasts of Middle-earth at strategic points, & established or expanded havens in places like Pelargir & Umbar that contested Sauron's power. He just never gained the power to beat them at sea by direct confrontation, which is one of the reasons that he subsequently submitted to Ar-Pharazôn the Golden.

Hope it helps!

All this is told in the Sil and UT. In short:

• Sauron was defeated through good generalship. He managed to destroy Eregion, but the victory was probably not a cheap one. Then (after a respite for hunting down Ringbearers) he turned on Lindon which was desperately defended by Gil-galad and his Númenórean allies (those that were stationed there) at the Lune. In addition his force was weakened by the necessity to leave a strong detachment behind which had to contain Elrond at Imladris. When massive reinforcements from Númenor arrived by fleet, part of that troops reinforced the Lune defence, making Sauron's position there untenable and he retreated. Another part of the fleet sailed southward and unloaded the remaining troops at Vinyalonde at the mouth of the Gwathló in an amphibious operation. Sauron's army was caught between hammer and anvil and annihilated. He himself narrowly escaped to Calenardhon. The army besieging Imladris was likewise wiped out.
• After this defeat in Eriador he let the West alone and focussed his activities on the rest of Middle-earth. He distributed the Seven and Nine Rings he had captured in Eriador to Dwaves and Men and began to build his empire. Thus almost all of Middle-earth fell under his dominion in these so-called "Dark Years" which lasted from SA 1701 to 3262 when he was brought to Númenor as a prisoner (since even his massive army was not able to defeat the might of Númenor, he feigned defeat and gve in to "captivity"). So for about 1,500 years, Sauron ruled almost all of Middle-earth apart from the Northwest and the western and southwestern shorelands which were colonies of Númenor. From 3262 to 3319 he corrupted the Númenóreans which led to the Downfall of that land.
• His fair form was destroyed in Númenor's fall and returned to Middle-earth as a disembodied spirit. Since he still had the One, he was able to quickly rebuild a body, re-organize his empire and prepare for war against the Realms-in-Exile founded by Elendil and his sons.
• Númenor slowly had developed imperialistic policies from ca. SA 2000 onward which were directed against the the teachings of the Valar (and the Eldar as their "friends"). The Valar themselves were at first ignored, rightly fearing their wrath.

Cheers
Tolwen

I do really and I found my knowledge on the details of Second Age events very poor so planning to re-read Akallabeth soon.

@Tolwen: Thank you once again now I have a clearer understanding but I wonder why did the Numenorians stopped at that point. They were still allies to the Elves and enemies of the Sauron at the time, I wonder why they didn't followed him into east and didn't continue fighting against him while he controlled the lands and distirbuted the seven and nine.

Couldn't even Elves continue fighting? I know they had heavy casualties but so does Sauron and we know they were a strong force in the Last Alliance many years later.

It is a question of necessity, political will and cost-benefit ratio. Penetrating further east would bring them ever more into Sauron's lands and become ever more dangerous. He can retreat using scorched earth tactics (as he did in the Last Alliance), making the campaign at some point moot and likely a total disaster. In a word, at the time they neither had the resources nor the will to push farther. Especially the Elves lacked both; IMO they had enough of war and were not willing to risk further losses and endanger their victory. One of the most important skills of a good leader ist to know when to proceed and when to stop. In the case of the SA 1701, there were no realistic gains worth the price of pressing on.
The Rings were top secret among the Elves at the time (mid-Second Age) and the Númenóreans very likely (IMHO that's absolutely sure) did not know about (and were not told by their allies) the Rings of Power at all.

The alliance at the end of the Age was exactly that: The Last Alliance. Both Elendil and Gil-galad were well aware that such an alliance was the last chance to stop Sauron. Waiting would mean strengthening the Enemy (Sauron still had not been able to fully rebuild his power when he struck Gondor) and eventually and inevitable defeat. It was a gamble where everything was risked and no reserves held behind. Either they would defeat him in this last hard, all-out push or they would be utterly defeated.
That war was no easy sledding, and eventually it dragged on for twelve years, including the vicious and brutal seven-year siege of Barad-dûr.

Cheers
Tolwen

And when did the Exiles learned about the One Ring? During the Last Alliance? Or was Isildur cutting it off was a coincidence?

IMO it is likely that the Elves finally came up with the truth during the Last Alliance. IMHO that's the point when the Númenóreans probably finally asked some questions...

Please note that I had a lengthy article about the Rings of Power in Issue #3 of Other Minds where this question is covered as well and in more depth. See the link in my signature for the place to download this and all other Issues (unless you already did )

Cheers
Tolwen

I am in the Facebook group but haven't read any of them yet. Will do now

I have read the article and it was very, very good. I enjoyed it greatly! Thanks for such a great magazine! I feel lucky to have all these issues to read now

Thanks for the feedback and your assessment of OM as a whole

Have fun reading it. I guess you also saw the PDF's of our predecessor magazine Other Hands? In OM Issue #10 you can read the story of its digital "resurrection"

Cheers
Tolwen