Here is a draft list of basic events & territory disputes. Please let me know your thoughts! ^^

-SunClan & CaveClan are the first two Clans to skirmish over territories. (Approx. 120 moons ago)

-Twolegs invade SunClan and kidnap some of the cats to become kittypets. The cats are never seen again. (Approx. 60 moons ago)

-Territory disputes between SunClan & CaveClan increase. (Approx 50 moons ago)

-Territory disputes arise between SunClan & MarshClan. (Approx 30 moons ago)

-Greencough ravages CaveClan (Approx 20 moons ago). They are now more cautious and reclusive towards the other Clans. 

-Badger invasion in SunClan. (Approx 13 moons ago) 

-Territory disputes between SunClan & MarshClan (Approx 10 moons ago). 

-Most recently, the territory disputes between SunClan & CaveClan have picked up once again. Currently SunClan and MarshClan are at peace, though they have had territory disputes as recently as 10 moons ago. CaveClan & MarshClan have not had known notable territory disputes.