In my opinion the best use of battle cry is to stretch your invasion ship out over multiple sectors allowing you to invade more sectors without losing your forward momentum due to ship position. ie the deeper into the opponents territory you push the further away your new kin will be losing initiative.
This way you can usually get by dropping 1 troop on each sector to capture using battle cry to boost the invasion on more well defended sectors (through either devs or natural defense)
Also its a great core-invasion card for any invasion ship that can get there (especially tech2 skink drop, you can put it in your tech deck if you want it for that ship specifically)
2 other things to remember are that great tree is also tech 1 and that a zero invasion kin is no threat at all to the opponent