Western governments are quick to call out Russia for committing war crimes when it causes civilian casualties in Ukraine, while exculpating Israel when it does the same in Gaza. But focusing only on whether the war itself in each case is legal, while ignoring the way the warfare is conducted, erodes a crucial distinction in international law, argues Hew Strachan.   

Russia’s war in Ukraine, and now Israel’s war against Hamas in Gaza, have intensified the already heated debate around the international law governing war. But the ways in which these laws are being cited threaten to distort the crucial distinction between ius ad bellum (the law governing the resort to war) and ius in bello (the law affecting war’s conduct).  Because Russia’s war is illegal, some presume that the way in which its armed forces fight is also illegal.  That may well be proved by due process, but legally fighting an illegal war doesn’t necessarily imply that the war is being fought in an illegal manner.