While there are a lot of memorable baddies in the Lord of the Rings universe, there are perhaps none that are more iconic than the Orcs. These creatures act as servants of Sauron, and are the evil forces that the heroes most often have to face off against. Despite the fact that they are so common and feature so heavily over the course of the series, their exact origins aren't delved into in the main part of the story, which has led many to wonder about where Orcs came from.
This history may not be the most important part of the story, but part of the fun of Tolkien's work is all of the lore that he created for it that perhaps spans farther than it ever needed to. Just because it wasn't a main plot point doesn't mean that Tolkien didn't have a plan for it somewhere, and he would often find ways to include these parts of Middle-earth's history that weren't consequential to the story, as it's a great way to flesh out the world building. So where exactly do Orcs come from, and what is their connection with the Elves?
Where Do Orcs Come From?
Throughout Middle-earth's history, Orcs served as the army for whatever dark force was in power, be it Melkor or Sauron. There are some different theories about where they originated, with The Book of Lost Tales claiming that Orcs were "bred from the heats and slimes of the earth" - aka from the ground through Morgoth's magic. However, as he was apt to do, Tolkien seemed to change his mind on this, which is where the most popular theory of Orcs being created from Elves comes from.
According to this theory, Orcs were initially created when Melkor first heard of the Awakening of the Elves, which was essentially the creation of the Elves by Eru Ilúvatar. Melkor sent evil spirits to worm their way in amongst the Elves, and these spirits planted seeds of doubt against the Valar. Some of the Elves were also captured if they strayed too far away, and they were taken to Utumno (Melkor's original fortress) to be tortured and made into Orcs, because Melkor wanted to make a mockery of the Children of Ilúvatar. This was how the early versions of the Orcs came into being, as far as most Tolkien fans can tell.
Later on, in the First Age, Morgoth bred thousands of Orcs to make them into an army to participate in the Battle of Bereliand, which lasted for nearly 400 years. Tolkien confirmed that there were female Orcs, which is how the mass breeding was possible. Even though they suffered defeats, particularly a large one in the Dagor Aglareb, Orcs continued to multiply, and even won some victories for Morgoth's side. They were almost destroyed in the War of Wrath, but those that survived fled to the East, into the various mountain ranges.
In the Second Age, Sauron appeared in Middle-earth again and made Mordor into his domain, where he kept his own army of Orcs. After losing battles to the Elves and Men because he hadn't been able to rally the Eastern Orcs, as they hadn't realized who he was, he went to them in a dark guise and was able to recruit them for his armies, thus building up his power. Orcs continued to be the backbone of Sauron's forces until his eventual downfall in the Third Age.
Are The Orcs In Lord of the Rings Fallen Elves?
In a way, the Orcs seen in The Lord of the Rings are fallen Elves because that's where the Orcs originated. However, they have moved quite far past that into being a species of their own that can multiply through breeding rather than new creation, so the Orcs of the Third Age aren't as related to Elves as one might think. A lot of Tolkien's world-building was unclear or never fully explained (or he himself changed his mind on it), so there are other sources that Orcs didn't come from Elves at all, mainly because Orcs aren't immortal in the way that Elves are.
In the Third Age (the time period of The Lord of the Rings), the Orcs that remained after the War of the Last Alliance were concentrated near the Misty Mountains. Once Sauron returned to Dol Guldur and his influence grew, the Orcs also began to grow in number. This is when a new, stronger breed of Orcs was created - the Black Uruks, made to fight against Men specifically. When the Dwarves abandoned Khazad-dûm, the Orcs moved into the halls, which created a massive war between the two races when the Dwarves attempted to drive the Orcs out of the Misty Mountains.
This conflict, plus the Battle of the Five Armies, depleted the numbers of the Northern Orcs, which made it so that they could not contribute as much to the War of the Ring (aka the main conflict in The Lord of the Rings). While all of this was happening, Sauron began building his army again and creating a stronghold in Mordor once more. His servant Saruman also created the Uruk-hai, the strongest breed of Orc to be seen yet, and these were the creatures that populated Sauron's army during the story. After the Ring was destroyed and Sauron was defeated, the Orcs scattered, and were eventually hunted to extinction by the time of the Fourth Age.