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Marley (マーレ Māre?) is a nation located beyond the Walls and across the sea from Paradis Island. Marley was once conquered by Eldia in ancient times, but during the Great Titan War, the Marleyans rose up and subjugated Eldia's territory, except for Paradis Island. In recent years, Marley sustains its global power using the power of the Titans, while attempting to cease Paradis Island to capture the Founding Titan and the island's natural resources.
Marley serves as the main antagonist to the Eldians inside the Walls and were the ones that filled Paradis Island with Titans.
Marley was a powerful nation in ancient times; however, this changed over 1,800 years ago when Ymir Fritz gained the power of the Titans. When Ymir passed away, her "soul" was split into the Nine Titans which were inherited by nine of her subjects who built the Eldian Empire. Using the Titans, the Eldians waged war against Marley and many other nations, utterly destroying them and obtaining complete rule over the continental mainland. This is considered to be the start of the Dark Ages.
Over an unspecified amount of time, Marley gradually gained control of the continental mainland that once was ruled by Eldia until only Paradis Island remained as King Fritz undisputed territory. In the year 743, King Fritz moved as many Eldians as he could to Paradis Island, and used the Founding Titan to guide a massive number of Wall Titans in the raising of three concentric Walls around Eldia's remaining territory. In order to force peace between Eldia and Marley, King Fritz gave the ultimatum that any further act of war against Eldia would be met with the releasing of the countless Titans within the Walls. With this, the Great Titan War ended.
Following the collapse of the Eldian Empire, the remaining Eldians of the mainland would then be forced into internment zones, where they would be treated as second class citizens. The nation of Marley would then utilize the Titan powers in order to become the world's major superpower. 
Marley would later recognize the Power of the Titans would not be enough to maintain its position as leader of the world in an age where military power is backed by fuel and began to turn its attention to Paradis Island which is said to have massive amounts of fossil fuels. However, the island is also home to the remnants of the former empire of Eldia, ruled by the Fritz family which possessed the Founding Titan.
While technological development on Paradis Island had been stagnant for a century due to King Reiss's isolation policies, the other nations of the world have already progressed far beyond it. By Grisha's early adulthood, Marley had reached the modern age and possessed technologies such as airships, early cars and planes, electricity, and photographs.
Eldian minority within Marley
The internment zones
After the Great Titan War, most Eldians who were stranded on the continental mainland were left at the mercy of an unforgiving Marleyan nation, which was nevertheless aware of the military potential of their genetic trait. To exploit it, the Eldians were segregated from the rest of the population into designated areas such as the Liberio internment zone under the watch of Marley's Public Security.
To justify its exploitation, Marley indoctrinated both its citizens and Eldians with a revised history which demonized the latter group. As a result, the Marleyan populace saw the Subjects of Ymir as evil due to their ancestor Ymir Fritz's deal with the "Devil of All Earth".
Compared to the Marleyan society beyond the fence, life inside the internment zones is lackluster but not poverty-ridden. For example, the Jaeger family was able to make a living working as doctors, a reputable profession. Nevertheless, they do have to endure abuse from the Marleyan authorities from time to time, which are occasionally lethal, as evidenced by the murder of Fay Jaeger. Movement in and out of the ghettos are also restricted, with the camp's main gate only open at a specified time of the day. One has to produce a permit in order to gain passage.
- The original Japanese name for Marley (マーレ Māre) bears a strong resemblance in pronunciation to the Latin word "mare," meaning "sea."
- Marleyan buildings bear resemblance to Italian architecture.
- Marley's policy of segregating Eldians into ghetto parallels the Nazi anti-Jewish policy. Similarly, many named Marleyans and Eldians have Germanic names.
- The history of Marleyans and Eldians is also comparable with that of the Rwandan populations of Hutu and Tutsi. By 1700, the Rwandan populace coalesced into around eight kingdoms, of which the Tutsi Kingdom of Rwanda became dominant and oppressed the Hutu, fueling a hard relationship between the two races that lasted for centuries. In 1994, during the Rwandan Civil War, the then Hutu majority government perpetrated a genocide against the Tutsi which resulted in the extermination of around 70% of the Tutsi population over the course of a hundred days.
- Since Isayama is Japanese, the Marleyan government's exploitation of ancient grudges for expansionist purposes might have been inspired by the anti-Japanese sentiment in China and Korea, where the memory of the Second Sino-Japanese War between 1937 and 1945 and the period under Japanese rule between 1910 and 1945 is kept alive by the government for nationalistic purposes. The landmass size difference between Marley and Paradis Island also reminds one of China and Japan.
- The memory alterations to people on Paradis Island to make them forget the past might have been inspired by the Japanese government's own attempts to downplay and deny Imperial Japan's war crimes.