We have no way of knowing. There's four possibilities:
1. It's a made up name, referring to a completely made up battle. One of the other CVEs is the TCS Enigma, and we don't know of any Marine landings there - but apparently, some took place.
2. It's referring to Khosan, but the name got misspelt at some point.
3. It's referring to Khorasan, an area covering north-eastern Iran, Turkmenistan and parts of Afghanistan. This seems the least likely option, since the region is not exactly famous for its involvement in any of the conflicts Forstchen usually refers to.
4. It's referring to Kherson, a strategic city near the Crimean Peninsula. I suppose there might have been some battles there, either during the Crimean War or during WWII. The difference in spelling might be attributed to transliteration, I suppose. If we assume that Khorsan was indeed a historical reference, then this is a likely candidate - but we haven't really got a reason to assume that.