Because conflict in the 21st century is all about asymmetrical warfare involving stateless combatants (and occasionally containing only stateless combatants) I was wondering what lessons we (NATO, UNSC etc) can learn from the Bush war, and whether we can tailor these approaches to peacekeeping style operations.
I've previously written an answer to a similar question here.
Needless to say, they worked very well as a military force but as a counter-insurgency force, they were actually downright awful. Unfortunately, the post-Bush War literature (often written by the RLI themselves) were quite happy to overlook this and if you browse the many armchair military forums around the web, you will see an almost insane amount of praise for the RLI - very much like how they praise the Waffen-SS.
What incredible results? The Lancaster House Agreement and the rapid transition of Rhodesia to Zimbabwe? I don't mean to bite your head off but this is an important matter that really speaks to the heart of your question: the Ian Smith government lost the war and failed to keep any of its political objectives in the aftermath, obviously their counter-insurgency strategy wasn't effective overall. It's much more instructive to look at the political reasons Rhodesian UDI failed than to lost cause the valiance or tactical proficiency of the Rhodesian armed forces.
Why, despite unquestioned conventional military superiority, was the UDI government forced to surrender? The short answer is international isolation, which produced a situation where the nationalist guerillas could base themselves in safe zones of neighboring countries and import Communist bloc military aid to their heart's content. The Rhodesian government had to mess around with sanctions busting and face continual difficulties in supply, to say nothing of the morale eroding exclusion from international sporting events. This political context creates an atmosphere of inevitability; when the rebels can operate across borders it's not possible to defeat them permanently by military means. The nationalists merely need to wait, and keep fighting, until their beleaguered opponents lose their resolve and the whole weight of international opinion comes down on the side of majority rule.
If there's one lesson counter-insurgents should learn from the Rhodesian Bush War it's the overriding importance of political factors. Counter-insurgents need to internalize what insurgents understand, what is the very foundation of the theory of guerilla warfare: that war is a continuation of politics that exists to achieve political aims. Political aims that are themselves impossible cannot be achieved militarily. When UDI was declared in 1965 the aim of white minority might not be quite impossible but it's pretty close to it, we are well into the era of decolonization and the erosion of British backing for its white colonial project..
It's an interesting counter-factual that if instead of UDI the white Rhodesians had pursued a more subtle program of white supremacy they might have maintained their power longer. Imagine that instead of blowing up relations with the U.K. and world by declaring UDI on the principle of white supremacy Ian Smith's government in the early 60s had paid lip service to equality while keeping land ownership and other prerogatives stacked in favor of whites. I think there are some other colonial contexts, British East Africa or Caribbean colonies, that suggest this would have been a much longer lasting way of maintaining white minority interests against rising nationalist claims.