I've been thinking about the Jagged knife, and this is my opinion of the Jagged knife throughout history. With these examples u would have to conclude they r realistic.
1. The southern kingdom of Judah came from Israel.
2, Carthage came from Phonecia.
3, Israel's conquering the holy land, and leaving tribes of everyone they conquered alive. There's even an example in the book of Judges of a man who tried to set himself up as king over Israel uniting the twelve tribes and failed. Israel rebelled against Rome and failed in 70 Ad. The united nations giving independence to palastine in the 60's. Israel evacuating the Gaza strip for the Palastinians.
4. Macedonia split into 3 or 4 kingdoms. The one that was not the main kingdom of Macedonia.
5. Pakistan from India.
6. Southern sudan.
7. The Gothic Invasion of the western Roman empire.
8. The crusade states during the crusades.
9. Any of the countries that split from the Holy Roman empire before the last Holy Roman Emperor, or the creation of the Vatican nation.
10, Any of the countries that gained independence from England or Britain, and got reconqered.
11. Any countries that gained independence in the New world that r still not a comon wealth. This also includes the Republic of California and the Confederate states of America. Originally Mexico included Central america and California, so this happened twice. Grand columbia included three nations and split up with Columbia keeping the name.
12, After world war 1 Europe was reorganized. Any of nations formed from Russia and Poland.
13. The vici French, but if u preferred u can say that is was conquered France instead. The Manchurian province that gained independence around this time for a short time from China. Since Austria still existed; the rest of the countries that were split up from the Austrian Hungarian empire.Taiwon after China became communists. Vietnam rebelling against the Japaneese occupation during world war 2 up to the end of the Vietnam war, and the reunification of the country.
14. After the breakup ot the Soviet union they gave back independence to the former Russian republics. The formation of Croatia and Bosnia from Yugoslavia if U count the Serbians as Yugoslavians like they insist.
There may be other, but the main point is that the Jagged Knife split from nations and the previous nation still exist. I would like to also point out that between Confederates and Hannibal that some of these guys could fight. This is my opinion of historical examples ofbe the Jagged knife.
Now I'm going to suggest a mega event or maybe an idea for a first encounter. Going off the fact that Aliens could be made from other solvients other than water, and might breathe other air than a Nitrogen and Oxygen mixture. Could lead to an accidental poisoning of some one like my offering u a glass of sulferic acid. On my planet this is like water to me, so u drink it thinking I'm not going to poison u. U die of course in a way it eats away at u. Upon examining U I notice 2 abnormalities suggesting u had a sickness maybe a plague, The first one looks like leprecy or burgers disease; because all life on my planet would be made from a lot of sulferic acid I could not imagine that this would be the problem. The other thing is I would notice that your body would be full of toxins instead of a normal blood suggesting poisoning by something that changes your blood to water. So I would quaranteen u and the other ambassador until I could do a full autopsy. The other species probably want to see the body and notice that u poisoned them. Because u tried to cover up the body by saying it was a quarenteen it would look like foul play. This could take place between two ambassadors upon first contact or between 2 regular people.
A event could be like when we met the native americans and gave them a plague that we were imune to smallpox.
These two events could cause an awkward situation when 1 of the above meets a species again. U would have an ambassador insulting the species like refusing peace offerings like food or drink. They may be entering the room with gas masks, Hasmatt suits, or breathing aperutus.