Sun Tzu says (to paraphrase), "If equally matched, we can offer battle, if slightly inferior in numbers we can avoid the enemy, if quite unequal in every way, we can flee from him."
Calling an invasion makes sense in that it offers activity and purpose to the writer base and characters. Yet the very real and reasonable response of counter invasion by the CIS followed by the authentic "righteous cause of exterminating a potential rival in it's infancy" by the TSE and their invasions force the Jen'ari to reevaluate their position.
So while I mourn the opportunity for interwriter collaboration and potential story offered through invasion, the Jen'ari had a choice.
Retreat, relent, and save their focus from the battles to come, even in the face of lost territory, or to risk burning out their writer base, having their characters overwhelmed, and demoralizing both IC and OOC if all fronts were fought for and lost.
So where some will cry cowardice, others may see the intelligence of cutting the potential greviously high cost of their invasion and the ramifications that followed and live to fight/write another day.