BlondieBC
Banned
Italy was militarily irrelevant. In both wars really.
Without Italy in the war, the Entente lose barring something really odd. The CP had a good second half of 1915, and without Italy in the war it gets even better. There is a whole chain of events that come from Italy not joining. Bulgaria likely enters early, which roles up Serbia faster. In mid-1915, A-H has about 10 more divisions to use or divert their supplies. Later in the war it is several extra armies. A-H went up to 55 year old men in the army. Here they will not have to go above 50. Economy works better. It avoid the blunder in 1916 by Conrad. With only one front to fight, he can't pick the least important theater. Romania does not enter the war with no great Russian offensive success. Even with this success they will be less likely since A-H has a lot more divisions hanging around the Romanian border or in reserve. In 1915, Russia will lose more land since there are more A-H divisions attacking them. Russia takes higher losses from mid-1915 to the end of the war. Russia is much more likely to make peace. Romanian grain makes the food situation better in the CP. Blockading in the A-H fleet is harder due to avoiding Italian territorial waters and not being able to use Italian ports. Italy probably sells weapons to the CP.
And a lot of these effects are cumulative. And it may be a bit easier to see if you look at a potential combination of them. Serbia is out of the war a few months earlier either to Bulgaria entering sooner or A-H just using available units not fighting on Italian border. Gallipoli goes worse for the Entente as Germany sends extra reinforcements. By the time Bulgaria enters IOTL, A-H forces excluding occupation forces are in Serbia on Russian front. A-H will attack Russia in the fall. Probably without great gains unless they can take Serbia fast enough to avoid the Germans losing the momentum in August. At the end of the year, A-H has taken equal or fewer casualties than OTL. Russia has taken noticeably more (over 100K + more) Germany will be similar. UK/France will have taken 10's of K more in Gallipoli. We can still have Falkenhayn's Verdun go similar to OTL. Likely better for Germany, but lets skip this one to given them some bad luck. It could go better, but it might be the same. Conrad will attack into the Ukraine. Only basic choice is to attack into the Ukraine. It will be less bloody for A-H than OTL and equal or bloodier than OTL. Romania will not enter the war. Falkenhayn does not get fired. So no USW. But let us assume this happens anyway for another bad break for the Germans. No USW means CP win. Period. End of Story, so this would be horrible luck.
At end of 1916, Russia has at least 1 million more casualties than OTL. A-H is same or lower. Food is much better. Germany will be equal or lower. France and the UK each will have 100's of K more casualties due to various small impacts. More supplies. Harder German attacks. A-H attacking hard in east frees up lots of German resources. Russia will not come close to lasting as long after the fall of the Tsar. So we get the H&L grand offensive in late 1917. USA troops are not there. Worse yet, with a lot more A-H troops around, even more German units can be freed up from other lines (East, quiet sections of Western Front). This will break French Army before USA becomes a factor on land in mid 1918. And this is a fairly negative case for the CP. It is likely that one of the small success I list for CP is big success. The offensive in 1915 goes much better against Russia. Gallipoli turns into a bigger disaster. Verdun works better/right. The A-H 1916 offensive against Russia breaks the Russian lines for a major success. USW does not happen. Falkenhayn stays in Charge which saves economy and gets not USW.