Revolutionary defencism, I think, is the most obvious. In Russia, the democratic revolution has won, Russia's allies are democratic England and France, in Germany and Austria-Hungary - the authoritarian imperial regime of the Kaiser and Emperor, so we need to defend our young revolution in a single democratic alliance from foreign reactionary occupiers.
In Germany, for example, the SPD took this position immediately after the war began.
1. Kaiser's Germany is more democratic than Tsarist Russia (true), so Germany should be supported as a more progressive force.
2. In Germany, everyone thought that Germany was defending itself. I know that this sounds strange today. I mean, World War I literally began with Germany declaring war on Russia. But in Germany, this was successfully presented as "defense against Russia, which was preparing to attack us first." Why did this sound convincing to the Germans: Russia was mobilizing at the time of the declaration of war. Why? Of all the countries participating in the war, Russia had the longest time to mobilize (a large country, bad railways). And the German Blitzkrieg Plan (Schlieffen Plan) implied a quick capitulation of France even before Russia had time to finish mobilizing. By that time, Austria-Hungary had already declared war on Serbia and begun its occupation - in response to this, Russia began mobilization and said that Austria-Hungary should immediately withdraw its troops from Serbia. The German General Staff began to panic - if they did not start first now, then after Russia's mobilization was over, it would be too late. So they conducted a media campaign about "military provocation on the part of Russia". Incidentally, it was precisely because the Germans sincerely thought that the war was defensive that the post-war conditions were such a shock and humiliation for them. Official recognition of the start of the First World War as Germany's fault? But we were the ones who defended ourselves! We were taken in by Wilson's fourteen points and promises of a fair peace! A bit off-topic, but I hope it was interesting and informative