It seems as if everyone has a new way of talking about war. Adjective changes like hybrid war, guerrilla war, revolutionary war, cyberwar, three-block war, and fourth-generation war compete with object changes like war on terror, war on drugs, war on poverty, and war on Christmas. Yet none of these really do a good job of defining their core noun—”war.”

What is war? This question is one of the basic exercises I’ve used with military students, including in my former position at the US Naval War College. These concepts are widely spoken of, and even more often misspoken of, which means the student responses can range widely—something not uncommon with easily identifiable concepts that are still poorly defined. The exercise works hard to educate and preclude sloppy thinking, but for those students who’ve finished the Naval War College’s Strategy and Policy coursework or any who are even passingly familiar with Carl von Clausewitz the quick and predictable answer is that “war is the continuation of politics by other means.” It’s such an easy and accepted answer, so the temptation is to dig no deeper and to move on; after all there’s a research paper to write. Yet, the question is intentionally broad and seeks to move past not only the inevitable student recitation of Clausewitz’s widely accepted dictum, but also the other common responses of “when Congress declares war” or “when someone is shooting at you.” Defining war is important for the lawyer, the theorist, the politician, the strategist, and the operator. Asking such a seemingly obvious question seeks to get past the other common questions of war’s nature, or war’s character, and into the larger conversation of what war is, beyond the notion that we know what it is even if we can’t easily define it. Occasionally someone will quote Shakespeare: “What’s in a name? That which we call a rose / By any other word would smell as sweet.” Even more astute students or faculty will compare the modern adjectivization of war with Lewis Carrol’s “Jabberwocky”—words that sound right but are eventually meaningless. Regardless, I’ve always been a little uneasy with the idea that all “war is the continuation of politics by other means.”

To start with, what are “other means?” Do an “other means” definition assert that Japan’s attack on Pearl Harbor was political? What about the attack on the USS Cole, the Khobar Towers bombing, or the 9/11 attacks? Were those political acts or were they war? Were they both? Or were any of them, as some want to apply the label, simply criminal acts? Can acts of war be criminal but also war? Is there a dividing line between politics and war? If so, what is it? And if not, then why did Clausewitz use the phrase “other means”? Or are these acts all part and parcel to the overall idea of “war”? Over time I’ve accepted a larger definition of war at the macro level. But at the less-than-macro (but not micro) level many still desire a means to differentiate types of wars and should do so with something other than just the tools of violence, the types of participants, or the war’s aims as distinctive categories.

Secondly, Clausewitz presumes that there is some line between war and peace. That is not a stretch when you consider that in Clausewitz’s time there was a clear, defined break between war and not-war. But today, look at the war in Afghanistan and the US-led invasion of Iraq. Clearly, neither action is one of peace, but neither “war” includes an official declaration from the United States or any other belligerent. Some might see this as a legal or procedural matter, but without a declaration it is easy for some to dismiss these violent, fatal, political actions and say they are not “war,” but rather overseas contingency operations, or some other superb substitute for something that might look like and sound like war, but just isn’t quite within the paradigm of state-on-state war embodied in, for example, World War II. Case in point, current actions in Afghanistan and Iraq are doctrinally foreign internal defense (FID) but does the soldier being shot at care about the distinction between FID and war? From the target’s perspective is a war declaration important? If there is no war declaration, how can the idea of “continuation of politics by other means” hold true? Should not the formal declaration of war be the bridge between “politics” and “other means”?

Clausewitz wrote his martial musings between 1816 and 1830. After his death they were edited and published by his wife, Marie. These writings, along with Sun-Tzu, Jomini, Douhet, Mahan, and Corbett, form the core canon for military strategists. Clausewitz’s dictum of “politics by other means” is so famous that in the narrowest search Google provides over fifty thousand returns. It’s famous, it’s well known, but in the modern world it is also wrong—or at least not completely correct. Why? Because modern states no longer accept war as an extension of politics.

That fact is explored in Oona Hathaway and Scott Shapiro’s 2017 book, The Internationalists, which describes the post–World War I push to make war illegal. It also provides context to help understand my uneasiness with the casual acceptance of Clausewitz’s dictum. Simply put, Clausewitz was correct for his time, but that was then and this is now. Today there is no distinction between war and not-war, as there was in the early 1800s and, large-scale, state-on-state war is so rare as to be a poor definitional construct. War is something else, something other than the extension of politics by other means. If war is extralegal, then sanctioned war is the continuation of law by other means.

Now, not everyone agrees with The Internationalists’ core precept of war’s illegality. But the biggest indicator that Hathaway and Shapiro are on to something important is in the now widely accepted notion that “war is the last resort.” This concept is not present in On War and likely did not influence von Clausewitz’ thinking but is omnipresent in modern American politics. Despite some foundation within Augustinian just war theory, the idea of war as the last resort only really gained traction in the 1970s with Michael Walzer’s discussions of just war theory. Regardless of when it occurred, a change is apparent.

If, as I assert, war is no longer the accepted extension of politics, the outlawry of war is insufficient to explain the differences between Russian action in Ukraine or Georgia and the American invasion of Iraq. One cannot simply declare war illegal and move on with the idea that any further violent military conflict is not “war”—decades of phrases like “range of military operations” and “military operations other than war” fail to resonate for a reason and get supplanted by gray-zone conflicts or some other equally unsatisfying phrase focused on tactics or techniques rather than the overarching concept. The importance of differentiating between types of war rather than types of weapons or tactics comes clear when Hathaway and Shapiro reach back to Hugo Grotius and the seventeenth century and identify what Grotius called “formal war”—state-on-state conflict within and in accord with the laws of nations. Formal wars were defined and involved exacting processes that began with a formal written document and often ended with a formal written document—destruction and bloodshed sandwiched between. In formal wars might made right, to the victor went the spoils, and so on. Grotius contrasted this with “informal wars” wherein there is no declaration, or one of the two (or more) parties is not a state, or where there is no state policy or authority—in effect, any war that was not a “formal war.” For Grotius, formal war has a clear shape—state-on-state, formal, declared, rules-based. Formal war is, principally at least, what Clausewitz was writing about. Formal war was the continuation of politics by other means. Today it is the continuation of law by other means.

However, the binary conceptualization of formal versus informal wars is also unsatisfactory for today’s lexicon. Once students get past Clausewitz and work into their own lifetimes they have difficulty integrating current operations in Afghanistan, Urgent Fury, Restore Hope, Odyssey Dawn, or historical actions like those in Vietnam and Korea into a concept of formal war. These combat actions saw no formal declarations of war, were not always state-on-state, and seemingly fit Grotius’s idea of informal war. Take for example the US invasion of Iraq. Was this a formal war? State-on-state, check. Laws of nations, check. Formal declaration . . . oops. But, it would be incorrect to call the invasion of Iraq an informal war because the war, at least from the allied side, operated under clear legal frameworks. What Shapiro and Hathaway helped me realize is that Grotius’s two categories are insufficient—that conflicts and military operations that do not fit our model of state-on-state formal war belong in either the informal war category (unlikely) or (more often) in a category I call “semi-formal war.” This third concept allows more nuance than the false binary of formal versus informal, and also allows us to recognize a spectrum of conflict for each belligerent.

Anyone who’s been invited to any function involving a question of attire knows there are arbitrary standards for formal, semi-formal, and informal (not to mention casual, business casual, business, dressy business, Warrior Wednesday, or Fleet Friday). Whichever way you break it down each standard involves some defined and cultural regime—either prescribed, proscribed, or both—and the standard is not fixed, but fluid. This is how we should approach the question of defining war, with Grotius’s analogy of formal and informal war (via Shapiro and Hathaway), along with the additional third category. War should be placed within one of three contexts—formal, semi-formal, or informal—based not upon the manner of violence, but upon the legal and political bases for the war, with a recognition that these, like the cultural regimes that dictate appropriate attire, shift over time.

Under this model formal war remains the traditional, conventional, normally understood definition of war where there is a declaration that ideally leads to an armistice or surrender. The laws of war apply to all sides. Treaties are in force and adhered to among all belligerents. While the victor determines the post-war outcome, everyone knows there is a legal regime undergirding operations. Formal war is where jus ad bellum and jus in bellum reside. Think of tails, bow ties, and engraved invitations.

Semi-formal war is what most of the world has seen since 1946. Korea was not a formal war—there was no formal war declaration by any belligerent. United Nations Security Council Resolution (UNSCR) 83 provided the legal recourse for conduct of the war against North Korea, but was not a formal declaration of war. North Korea, until 1957, was not a signatory to the Geneva Conventions and did not follow them in form or spirit for soldiers captured during combat. UNSCRs play prominently in other post-1946 conflicts—Desert Storm, Odyssey Dawn, and the 2003 invasion of Iraq to name a few. The United States’ current operations in Afghanistan and the 2003 invasion of Iraq are semi-formal wars. The Argentine invasion of the Falklands and subsequent British recapture was a semi-formal war. Semi-formal war is the overt or tacit compliance with international convention for at least one side of the conflict. In semi-formal wars, the elements of formal war exist but they are not completely met. You might dress up or dress down, but there are still some clear sets of rules in play.

In informal wars, one or both or all participants don’t rely on a legal framework for action and are not overly concerned with lawfulness. They are not truly state-sanctioned in the sense that a formal declaration of war has been made, even if one, or both, sides is state-sponsored. Participants don’t really fixate on catchy Latin phrases or worry about treaties—especially and specifically the Geneva Conventions. The ongoing Mexican Drug War, the Rwandan genocide and Rwandan Civil War, the American Indian Wars, the Sri Lankan Civil War, most (if not all) insurgency/counterinsurgency actions but especially large portions of conflict in the Philippines (1899–1902, 1942–1954, 1969–present), El Salvador (1979–1992), Colombia (1964–2017), Northern Ireland (1960s–1998), and Afghanistan (between the Afghanistan government and the Taliban) are informal wars. Informal wars may, and often do, exist within formal or semi-formal wars. With informal wars anything goes—from Daisy Dukes to tuxedo t-shirts. The broad nature of informal war makes the easy binning of wars difficult, but three categories is still better than the all-or-nothing binary of formal and informal. It’s also a time to remember that both sides in a conflict may see the engagement from different models. Just because the United States desires a formal affair does not require the opposition to act in the same manner.

In keeping with the analogy of proper attire, given American governmental inclination for lawfulness I see no world in which the United States ever openly engages in informal war. Here the additional concept of “dressing up” but not “dressing down” applies. Even covert actions will seek some form of legal support to absolve the participants of legal liability. This adherence to international norms and conventions might mean that the United States is wearing a cummerbund and bowtie underneath that sport coat or Hawaiian shirt, but the formality is there nonetheless. And, in any case, categorizing wars is less about knowing what type “we” are in but in understanding what rule set the adversary is in—of understanding an important part of the operational environment. Whether one is in a formal, semi-formal, or informal war depends on both your own perspective and that of your adversary. Or, in military platitude, the enemy gets a vote. We must know whether our adversaries ascribe to our cultural, international, and legal norms, or not. Assuming they do just means we are left looking foolish critiquing their dress while they know what sort of party they showed up to.

The dual concepts of formal/semi-formal/informal and us/them, together, are useful for strategists, politicians, and war planners who first must always know what their forces’ constraints and restraints are and must also know what the adversary is likely to do. Deciding what to wear comes before deciding on a menu or entertainment—where the menu or entertainment are akin to the adjectivization of war. Before deciding is something is a hybrid war, is it formal, informal or semi-formal. Before asserting that we are in a cyberwar, are we wearing shorts, a suit, or tails? Why? Because unless we recognize the legal constraints and authorities that we and our adversary operate under we will make a mistake.

We must also recognize that not all conflict is “war.” Trade wars, the war on drugs, and the war on poverty are rhetorical flourishes designed to evoke a feeling of commitment to action and not a commitment to violent action. Likewise, not all state-on-state conflict is war—it is often politics by other means, with those other means now including legal wrangling, economic and diplomatic coercion, and the possibility, however slight, of actual combat hovering in the background. Let us look, briefly, at the current return to peer competition, which—if any context does—provides an opportunity for formal war.

Those who argue that war with China is unlikely are largely thinking of formal war with all of its process and formality. Meanwhile those who think it likely are occupied with semi-formal war or misinterpret non-war actions as war-like. China however, recognizing that some world order which they were not part of outlawed war, is paving its own path by exploiting seams in law, convention, and treaty, but also leveraging historical lessons of gunboat diplomacy—not to force acceptance of a treaty but rather to preclude action by otherwise law-abiding nations. In a legal regime where possession is nine-tenths of the law, China is playing by a different rule book, and we must decide whether to continue playing by misunderstood pre–Kellogg-Briand ideas where force is accepted or within a modern rule set where force is a threat, but a rarely used one, and whoever throws the first punch is typically wrong.

Much is written about Clausewitz’s views on policy and also his recognition that war’s nature is constant while it’s character changes with time. The idea of formal, semi-formal, or informal wars is neither about the nature or the character but instead seeks to move war from being the “continuation of policy by other means” to the “continuation of law by other means.”

So, the next time someone asks, “What is war?” get past citing very smart but long dead thinkers and start your own thinking. What is the rule set? Who is involved? What are the parties’ actions? In effect, what should I wear to the war?


Capt. Michael Junge, PhD, is a US Navy Surface Warfare Officer who most recently taught Leadership and Ethics at the US Naval War College. He commanded USS Whidbey Island (LSD 41) and served in amphibious assault ships, destroyers, and frigates. He is the author of Crimes of Command in the United States Navy: 1945-2015, a review of post-World War II naval accountability.

The views expressed are those of the author and do not reflect the official position of the United States Military Academy, Department of the Army, United States Naval War College, United States Navy, Department of the Navy, or Department of Defense.


Image credit: Tech. Sgt. Patrick Evenson, US Air National Guard