The owner of the land is whoever can hold it using force. There is no land claimed by anyone that doesn't either have the army to fend off all neighbors, or a big brother behind them waiting to back them up.

Time is irrelevant. Claiming to be the first in an area is irrelevant. If you can fend off say... 8 or more countries with enough force to render their army null and void in 5 maybe 6 days, then that land is yours until its taken by someone with more force than you.

Nothing is rightfully anyone's property unless you can defend it.