The Spring Sea is a major body of water located in Strangereal's southern hemisphere, and is a component sea of the Atlantic Ocean. It is connected to the Cascade Ocean in the north, the Aurelian Sea to the southwest, and the Eusian Ocean to the east. The Spring Sea is bordered by several nations, including Erusea, the Nordlands, Wielvakia, Ratio, and Sapin.
On September 14, 2019, the Osean Defense Forces conducted Operation Fisherman in PX80443, which aimed to sink the rogue Erusean nuclear submarine Alicorn. During the operation, the Alicorn attempted to fire a shell at Oured, however, due to Osea jamming its terminal guidance, and Trigger throwing the barrel off, the shell missed its mark. The submarine was sunk by Trigger shortly afterward.
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- SP Mission 03: "Ten Million Relief Plan", Ace Combat 7: Skies Unknown.