But then one event happened which made this dangerous travel in hostile lands unnecessary. It also forever changed the military equations of Middle-Earth. The Orcs made a chariot which was not driven by horses or wolves. Instead of being propelled by beasts of burden, it was propelled by fire. The Orcs called these chariots “wahan”, meaning that which carries.
These wahan could travel faster than any stead, or anything in middle earth. As the tools of the Orcs got better, the wahans became more sturdy and faster. In the times to come, these were to become the weapons of choice for the Orcs.
Now the Orcs could outrun any enemy and the travel between Moria and Mordor became much faster and much less dangerous. This greatly benefited the Orcs, on either sides of Anudin. The Mordor Orcs got the much needed mithril and the Moria Orcs got better tools, armor and weapons unsurpassed in quality in middle earth and wahans. By now, everyone in middle earth was aware of the power of the Orcs. The Elves tried to renew old alliances against the Orcs, but the Orcs had decided never to ally again with the Elves.
With the Elves forming new treaties against the Orcs, the Orcs signed a mutual non aggression pact with the Dwarves. The Orcs ceded parts of Moria to the Dwarves.
The alliance of men of Gondor and Elves was reformed. But many elves had already crossed the sea, and their numbers had dwindled. The alliance marched on to Mordor. But this time they had underestimated the power of Orcs. In their wahans, the Orcs poured out of Mordor and Moria in large numbers. They not only repulsed the attack but started occupying territories not previously theirs.
The war made the Elves and the Gondorians realize that the Orcs now could not be taken lightly. They asked the Valars for their help. But the Valars were asked by the Illuvatar not to meddle in the affairs of Middle-Earth. The Valars asked the Elves to come instead to Aman. But leaving the Gondorians at this time, without any allies would have amounted to treachery. So the Elves stayed behind to help in the war.
The Dwarves remained aloof of all these hostilities, joining neither the Orcs nor the Elves. The Orcs crossed the Anudin and overran parts of Gondor.
On the other front, the Orcs of Moria laid siege to Rivendell and the adjoining areas. The siege lasted for a long time before it was finally defeated. Help came to Rivendell from the most unexpected of the places. Tom Bombadil himself left his forests to defend the Orcs. With his help the hosts of Arnor and Hobbiton broke the siege of Rivendell.
But before that, the Orcs reformed their old alliances with races which had supported it in the previous wars. The alliance marched on to Rohan and other areas before it meet another totally unexpected foe, the Ents along with their Ent-wives. They now greatly increased in numbers proved to be an insurmountable barrier. The wahans of the Orcs could not crush them and their crossbows could not pierce their thick skin.
Now a stalemate was reached on all fronts in middle earth, with no side being able to get an obvious advantage. Both sides retrenched their positions and waited. Both sides were being bled financially and materially, without any obvious gains.
The second great winter of Middle-earth started during this time. The lakes froze over and all greenery wilted. There was shortage of food all over.
With resources barely enough to eat a ceasefire was called by all sides. All the races met and decided to stop the war then and there. The elves tried to negotiate a position where everyone got a place same as that before war, that at start of middle earth, but ultimately had to settle for status quo.
The winter lasted for forty years and no wars or hostilities were done during this time. As the winter receded, the need to maintain the ceasefire passed. But by this time the society and the economics of the races had so intermingled that no race could afford to strike other without seriously damaging itself. As summers came back to middle earth, and prosperity returned, the races joined together and formed the council of all races. All races were represented. This marked the end of the fourth age and beginning of the fifth. A age where financial and political power was much more important than military.