Among figures in Finnish history, Mannerheim is one of the most important ones, and not without merit. His involvement has left both a mark on Finnish history and the nation’s consciousness due to his roles in the Civil War and conflicts during the WW2 (Winter, Continuation and Lapland) and is one of those few historical figures people not that interested in history can name.
So, what if he had never existed? While he did have colourful career before the Finnish Civil War, I don’t think his non-existence would have much effect on things before 1918. The Russo-Japanese War wouldn’t go differently if Russia lacked one Finnish colonel and same goes to campaigns in Galicia during the WW1 when he was a lieutenant general. His time as a spy in China between 1906 and 1908 and drafting of Russian military plans regarding Northwestern China were probably his greatest contribution to history before the Civil War as a single individual but I don’t think he was irreplaceable in that role.
This brings us to the Finnish Civil War. How would that war go if there wasn’t Mannerheim? I think one big contribution Mannerheim made to the White Guards was the fact that he was able to make it a cohesive force, even though there existed many fault lines. There were the jaegers, Finnish young men who had secretly travelled to Germany to train and fight in that country’s army; there were those who had served at the Russian Army (just like the Mannerheim) and who were untrusted by many Finns; and there were also Civil Guards, a militia force which had risen before the Civil War. You might even add those men who had served in the Finnish Army which had existed before 1901. Getting all these people to work together wasn’t very easy and there existed a great amount of distrust between these groups, especially jaegers and former Imperial Army officers. Even if Mannerheim had served in the Russian army and wasn’t entirely trusted by all, he was respected enough to get everyone else to follow his plans. If it wasn’t for Mannerheim, it seems very possible that the organization of White Guards might have suffered and there might have been more infighting. The fact that he was Swedish-speaking might have also healed some potential fault lines among the Whites, even though they didn’t disappear.
Other big difference might be Finno-German relations. Mannerheim himself was reserved towards German. Without Mannerheim, the Whites might become even more pro-German than they were IOTL. The Vaasa Senate might ask for German help more forcefully and might be more willing to let Germans to take a more visible role in the victory. Especially the jaegers were willing to let Germans to have a larger role in the War.
What are your thoughts on this topic? Do you have some person in mind who could have taken Mannerheim's role as a White General and how his way of waging the War might have differed? What sort of post-war effects there might have been?