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One option for a coalition war in Europe could be in the aftermath of the 1848 revolutions, even if they are mostly suppressed, could be this:
"After the Austrian Revolution was suppressed, an Austro-Russian war against the Ottoman Empire seemed imminent. The Emperors of both Austria and Russia demanded that the Sultan return Austrian rebels who had sought asylum in the Empire, but he refused. The indignant monarchs withdrew their ambassadors to the Sublime Porte, threatening armed conflict. Almost immediately, however, Britain and France sent their fleets to protect the Ottoman Empire. The two Emperors, deeming military hostilities futile, withdrew their demands for the surrender of the fugitives."
What if the Austrians and Russians mistakenly presumed the British and French are bluffing and attack the Ottomans, ending at war with the Ottomans, France Britain and Sardinia?
The Prussians can be aligned with Russia and Prussia for mainly ideological/monarchical solidarity (although I think the Austrians would have to grant the Prussians some sort of concessions within the context of German dualism to get committed Prussian help). https://en.wikipedia.org/wiki/Eastern_Question#Revolutions_of_1848
Alternatively, Prussia can keep itself neutral and insulate non-Austrian Germany and much of northern Europe from a war raging mainly in Italy, Balkans and the Black Sea area.
Or, Prussia, irritated by a lack of respect and concessions from Austria, can join the Franco-British-Ottoman-Sardinian alliance. The problem there is I see a major overmatch ending the war sooner with fewer casualties than the OP's challenge.
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A second option could be Adolphe Thiers getting into a war in the 1840s by carrying out his threat to aid Muhammad Ali both directly and indirectly by invading the Rhineland. -- Or him doing an intervention in Spain, and having other European powers come in against him. --It would take the monarch having a different attitude for either scenario to happen.
"His policy of support for Muhammad Ali of Egypt in the Eastern crisis of that year led France to the brink of war with the other great powers. In addition, Thiers favored military intervention in Spain's civil wars, but all of these met with the disapproval of the king who supported a completely pacifistic foreign policy and he was soon dismissed from his post."
https://en.wikipedia.org/wiki/Adolphe_Thiers#July_Monarchy_of_King_Louis-Philippe
One option for a coalition war in Europe could be in the aftermath of the 1848 revolutions, even if they are mostly suppressed, could be this:
"After the Austrian Revolution was suppressed, an Austro-Russian war against the Ottoman Empire seemed imminent. The Emperors of both Austria and Russia demanded that the Sultan return Austrian rebels who had sought asylum in the Empire, but he refused. The indignant monarchs withdrew their ambassadors to the Sublime Porte, threatening armed conflict. Almost immediately, however, Britain and France sent their fleets to protect the Ottoman Empire. The two Emperors, deeming military hostilities futile, withdrew their demands for the surrender of the fugitives."
What if the Austrians and Russians mistakenly presumed the British and French are bluffing and attack the Ottomans, ending at war with the Ottomans, France Britain and Sardinia?
The Prussians can be aligned with Russia and Prussia for mainly ideological/monarchical solidarity (although I think the Austrians would have to grant the Prussians some sort of concessions within the context of German dualism to get committed Prussian help). https://en.wikipedia.org/wiki/Eastern_Question#Revolutions_of_1848
Alternatively, Prussia can keep itself neutral and insulate non-Austrian Germany and much of northern Europe from a war raging mainly in Italy, Balkans and the Black Sea area.
Or, Prussia, irritated by a lack of respect and concessions from Austria, can join the Franco-British-Ottoman-Sardinian alliance. The problem there is I see a major overmatch ending the war sooner with fewer casualties than the OP's challenge.
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A second option could be Adolphe Thiers getting into a war in the 1840s by carrying out his threat to aid Muhammad Ali both directly and indirectly by invading the Rhineland. -- Or him doing an intervention in Spain, and having other European powers come in against him. --It would take the monarch having a different attitude for either scenario to happen.
"His policy of support for Muhammad Ali of Egypt in the Eastern crisis of that year led France to the brink of war with the other great powers. In addition, Thiers favored military intervention in Spain's civil wars, but all of these met with the disapproval of the king who supported a completely pacifistic foreign policy and he was soon dismissed from his post."
https://en.wikipedia.org/wiki/Adolphe_Thiers#July_Monarchy_of_King_Louis-Philippe