Purely ‘defensive weapons’? There’s no such thing for Ukraine or anywhere else

The FGM-148 Javelin anti-tank missile is the sort of ‘lethal defensive weapon’ the US may consider supplying to Ukraine. Wikimedia Commons/US Army

US President Barack Obama said recently that supplying “lethal defensive weapons” to Ukraine is one option if a diplomatic resolution of the conflict with Russia fails.

This sounds like a measured and sober proposal because the weapons are defensive, presumably needed to counter offensive weapons wielded by Russian separatists. However, even so-called “defensive weapons” can be deeply problematic.

Defence may be burdensome, divert resources from productive and useful exercises and sometimes be “lethal”. But many people consider this justified because one is presumably always allowed to defend oneself.

Military institutions, and the governments that support them, need justification and do so by invoking defence at every turn. So “defence departments”, “defence forces” and “defence science and technology organisations” are necessary, although in an ideal world without conflict we would do without them.

Why are ‘defensive’ weapons seen as good?

Defensive weapons are seen to be “good” because they are the means by which we defend ourselves. Supplying them to others is justified if they are subject to aggression.

However, it is surprisingly difficult to come up with an example of a weapon that is purely defensive. A tank or helicopter or assault rifle can be used to defend, but all of these can also used for aggression, so surely do not count as defensive weapons in the requisite sense.

Obama might have meant that he would supply Ukraine with weapons that can be used for defence. But virtually all weapons can serve this purpose, save perhaps nuclear weapons. This implies that there are simply “weapons”, which can be used for this or that purpose, for defence or for aggression.

One problem with supplying weapons understood this way is that these can be used for aggression at a later date. They may be captured – Islamic State is using sophisticated US and Russian weapons in Iraq and Syria. Or they may be turned against those who supplied them – Norway sank the German cruiser Blücher in 1940 with German-made guns. There are many such examples throughout history.

What defensive weapon cannot also be used for attack?

As a context for these comments, I will suggest two definitions of a defensive weapon. One expresses what seems obvious about defence, but does not serve to justify the design, manufacture, provision etc of weapons as unproblematically “good”. The other does provide justification if any weapon conformed to it.

  1. A defensive weapon is one that actively defends an asset.

  2. A defensive weapon is one that cannot in any way aid aggression.

Virtually any weapon can satisfy (1). For instance, the Wehrmacht used essentially the same weapons when it was on the defensive and retreating from the Soviet Union between 1943 and 1945 as it did when on the offensive in 1941 and 1942.

However, to my knowledge, no weapon satisfies (2). Such a weapon would have to be fixed in place and programmed only to work if the asset in question were attacked, and not be movable or reprogrammable. But such a weapon could, if it existed, still aid aggression.

The Russian Buk M air defence system, which is believed to have shot down flight MH17 over Ukraine. Wikimedia, CC BY-SA

Defence and the levels of strategy

Edward Luttwak’s account of the levels of strategy can help us understand how confusions about defence come about. No military campaign of any duration can be continually on the offensive. Referring to the Second World War again, the main attack on the Soviet Union paused in August 1941 when the German tanks needed to be refitted and the Soviet forces, equipped with many tanks, went on the offensive.

Also, a country engaged in aggressive war needs to defend its civilian assets at home as well as its military assets in the field.

In Luttwak’s terminology, the Wehrmacht was using defensive tactics in August 1941, which were embedded in an offensive operation. This was in order to achieve an offensive theatre strategy, while the converse was the case for the Soviet Union.

“Levels of strategy” refer to the size and scope of military engagements, the lower being subordinated to the higher as a means to an end. The very lowest level, the technical, refers to the characteristics of the weapons available. These will determine the particular tactics they can be used for.

The Soviet Union was fighting a just war and Germany an unjust one, because the former was defending itself and the latter was the aggressor. But it does not follow that the Soviets employed a special class of weapon, defensive weapons: weapons that could only be used for defence.

Mixed meanings for mixed uses

So if Obama supplies weapons to Ukraine for the purpose of thwarting attacks by Russian separatists, then this could be their only employment. Alternatively, the separatists could capture these weapons and use them for further aggression against Ukraine government forces. Or Ukraine could prevail and use the weapons to take back Crimea.

These last scenarios are unlikely, but they are not made impossible, because the weapons are not “purely defensive”. When governments and “defence” departments and forces use such terms we should not be fooled into thinking that the means they have available can only be used for this end.


Editor’s note: John will be answering questions between 11am and noon on Wednesday February 24. You can ask your questions about the article in the comments below.