"If you tell a lie big enough and keep repeating it, people will eventually come to believe it." Some ascribe this quote to Nazi propagandist Joseph Goebbels; others say Hitler authored the idea. In Mein Kampf he did speak of the invention of a lie so "colossal" that few would believe that someone "could have the impudence to distort the truth so infamously".

Whoever coined the idea, the point is this: controlling the narrative matters immensely.

Military prowess is not enough in this age. And the United States knows it. America's "other army" – its less visible but equally potent cadre of skillful lawyers (in government and even in private institutions) – dutifully got busy crafting appropriate international law narratives for the War on Terror. They realized that winning the battle for defining "legality" on the world stage was critical.

This is something states in the developing world would do well to understand. And particularly, governments of countries that bear the brunt of US military interventions touted as "self-defense" and "counter-terrorism" – Pakistan, Yemen, Somalia, Afghanistan and Iraq. Such states need to build intellectual-professional capacity to counter precedent-setting international legal arguments strategically employed (or better said: deployed) against them.

No contemporary political discourse provides us with a clearer illustration of this than the heated debate about the (ill)legality of drones and targeted killings.

For the past decade, the United States strategically weaved a narrative of legality around, apparently, "surgically precise" drone strikes. It confidently claimed that strikes fully complied with international law, even as Pakistan objected to them and evidence mounted that women and children had been killed.

Academics, including myself, argued against this simplistic black-and-white narrative. So did UN Special Rapporteurs and others. In contrast, there were many legal minds in the United States, often with a history of US military or government service, who agreed with the government. Rather controversial and unsettled legal arguments were swiftly dug up and supplied to justify and provide legal bases for geographically and temporally expanding the "War on Terror". This includes the idea of "co-belligerency" (wherein a third party state or non-state actor that does not declare neutrality can be considered a belligerent as well), and the unwilling or unable doctrine that says that since target countries can't or won't prevent threats against the US, attacks within their sovereign territory are legal.

Some lawyers in America were, for example, quick to simply assume Pakistani consent to drone strikes on the basis of highly circumstantial evidence. But, conversely, rather slow to recognize that "coerced consent" was a more fitting description of the facts. Other, similar patently obvious political realities were ignored. The hugely asymmetrical power of the United States vis a vis the nations it was attacking or "seeking" consent from, or the fact that hundreds of thousands of non-Americans – far, far, far more than Americans killed by terrorist groups – had been killed as a result of the exercise of "lawful" self-defense by the US since 9/11 – through drones and otherwise.

But this is not surprising. Perhaps the role of international law was not really to ensure equity in the international order or constrain force in accordance with the spirit of international law, but conversely, to provide strategic "legal" fodder for a state that seemed to have an insatiable appetite for undertaking "self-defense" abroad.

Thankfully, the legal debate is far more nuanced today than it was in previous years. Amongst others, UN Special Rapporteurs (pdf) and human rights organizations (pdf) have weighed in and exposed the fragility of the US narrative. In fact, even ordinary individuals who previously had no interest or knowledge of international law are now curious to know what global law says about interventions, drones and even military occupation.

So, kudos to the United States for, rather ironically and unwittingly, encouraging this unintended interest in international law in the global popular imagination.

When I visit Pakistan, people ask me, often with some indignation, how international law could grant the United States a license to unilaterally attack other states in a perpetual war in which so many Pakistanis, Afghans, Iraqis and others had died, even as the attacking state's nationals lived a comfortable "war-free" existence a couple of continents away? What, they asked, was the point of such law if it basically permitted interventions in sovereign countries?

I tell them the reality is that international law is not really that callous. It is self-serving, strategic interpretations that the United States constantly pushed through as part of its narrative that made it seem so. There's a difference between the law and the American "interpretations" of it.

But really, the long-term lesson for the people and governments of other third world states is this: don't underestimate the power of narrative and legal rhetoric in international affairs. Until you build capacity to counter the dominant narrative and promote competing interpretations of what is "legal" in international law, you will continually be outwitted in international affairs, not just on the battlefield.

Even Vladimir Putin – with all his shrewdly strategic talk of upholding international law in the New York Times – knows this.