US and TPLF are not friends - unless you mean Tigray are Jews
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If Abiy does a clean job in Tigray and take a clean shot on TPLF avoiding civilian causalities; nobody will give a damn about Tigray.
The problem is Abbiy and Ethiopians want to commit genocide against Tigray - and few people will allow that.
Abiy has to professionally fight TPLF - reduce civilian causalities - avoid mass graves - allow UN food aid to flow - allow medicine to flow - and engage TPL fighters.
If he does that - and beat them - that is clean war that US and EU will have no problem with - combatants versus combatants.
Ethiopia gov already enjoy disproportionate advantage in everything - troops, money, ability to procure weapons, air force - it has no excuse to fight like bunch of rebels
US Wont allow for the full destruction of TPLF rather they will keep them alive to destabilize the HOA and Ethiopia whenever they feel like. But TPLF days in Ethiopia are gone.