I tried but couldn't find info on the 濟 dynasty in English. In Korean it's known as 제나라 (Je dynasty), and was founded when in 765 AD by Yi Jeong Gi 이정기 (李正己 ), a Goguryeo descendant and his Goguryeo refugee followers killed the governor and built a base in Shandong. He stated that he was not a Tang, but a Goguryeo person. His son Yi Nap 이납(李納 ) proclaimed an independent nation in 782 and became King. expanded great area of land, even threatening the Tang capital.
This was the early expansion of the dynasty, indicated by red arrows, as starting from the Yeongju area at the top where Goguryeo prisoners were held, and their landing in Shandong. Eventually they gathered enough strength, 100,000 soldiers, to threaten the capital Chang an, to the left.
And the full extent
The Je dynasty maintained independent ties to Silla and Balhae, became very wealthy thanks to intermediate trade. Later on Silla even sent 20,000 troops to aid the Tang in defeating the Je dynasy, in 819
This was the early expansion of the dynasty, indicated by red arrows, as starting from the Yeongju area at the top where Goguryeo prisoners were held, and their landing in Shandong. Eventually they gathered enough strength, 100,000 soldiers, to threaten the capital Chang an, to the left.

And the full extent

The Je dynasty maintained independent ties to Silla and Balhae, became very wealthy thanks to intermediate trade. Later on Silla even sent 20,000 troops to aid the Tang in defeating the Je dynasy, in 819
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