Rule, Britannia !
As an unrepentent old Imperialist, I can only say that, if you really want to influence a country, you have to take over its government - by force, if that's the only way. Then rule kindly, if you can; harshly, if you must - but always rule. (I'm aware that this opinion will entail my excommunication from the ranks of the Great, the Good and the Politically Correct).
Any other form of "intervention" will be (a) ineffective, (b) certainly unrewarding and (c) you will probably come out with a bloody nose. The last few hundred years should have taught us that.
If you must "intervene", then go in with a firm purpose and enough military force to impose your will (and some idea of how to get out if it all goes wrong would be helpful, too).
Always remember the Parable of the chap who got rid of one devil and ended up with seven other devils worse than the first. (Aren't we seeing this now ?)
(Oldest Inhabitant subsides muttering into his chair in the corner of the Bar. Another pint, Grandad ?... Thankee kindly, son ! )