The challenge is to have the Japanese conduct joint or coordinated operations as allies in a war
I think this challenge is the most difficult of the two.
Here's what I can come up with -
1. France and Britain fail to develop a positive trend in relations from 1901-1904, failing to reach the Entente Cordiale of the latter year. Causes could be plentiful. France could walk out of the Fashoda crisis or the Boer War tensions determined to built a bit more naval bargaining leverage. King Edward may not be as touristic and Francophile as he was in OTL. Perhaps there is a perceived clash of interest brought on by either Britain or France getting too grabby about parts of Siam. Regardless, by 1904, there is no Entente Cordiale.
But the Germans have also held aloof from the British alliance offer, and Britain, from any German designed counter-offer.
Britain does have, and relies on, its Japanese alliance. France does have, and relies on, its Russian alliance.
The Russo-Japanese War breaks out in 1904 with the Japanese attack.
The Dogger Bank incident occurs, but has worse casualties.
Consequently the British DoW the Russians. The Russians try to make an escape to French and neutral ports. Hardly any of them make it, with nearly all their Baltic vessels on the open ocean being overtaken and sunk or captured by the royal Navy.
The British initiate a merciless war against Russian merchant shipping and a paper blockade against Russian trade. Russia invokes its dual alliance casus foederis with France, calling for aid against Britain.
France initially does what it can to help Russia economically, calls for a halt to Anglo-Russian fighting, and offers to mediate, hoping to keep its Russian alliance without having to go to war.
When Britain is recalcitrant to this (and Russia isn't abjectly conceding to British demands and Japan's now escalating demands), France declares war on Britain and Japan.
Britain takes the lead on challenging the French fleet, attacking French commerce, and establishing an anti-French paper blockade. Britain also grants additional loans allowing Japan to sustain and step up its ground and sea war effort to keep up its pressure on the Russians, and encourages the Japanese in more borrowing in the United States.
Within Europe, neither coalition is offering sufficient incentives, nor safety, to encourage Germany or its ally Austria-Hungary to abandon neutrality. Germany uses its weight, attractiveness as an ally, and fearsomeness as an enemy, to ensure respect for its neutral rights.
Germany is able to continue land trade with France, Russia, and all its neighbors, and quickly makes money supplying many industrial goods formerly provided by British exporters (as do the Belgians). Germany, whose friendship Britain desires, is also able to ensure its trans-Atlantic and trans-oceanic trade is unmolested by British blockade.
Versus the Russian fleets, Britain is capable of masscaring any Russian fleets or combatants on the open ocean in the seas that venture out beyond the protection of heavy fortress guns. So the residual naval forces in the Baltic and White Sea/Arctic are soon hors de combat, as the Japanese have basically finished off the Russian Pacific fleet.
Only the Black Sea fleet, for the moment protected behind the Turkish straits, remains for the Russians. Meanwhile, the British chasing, destruction and bottling of the French fleets is a more time and labor-consuming process.
The British mobilize forces in India, and the Russians mobilize forces in Central Asia to deal with any contingency threats from each other. The India forces are also oriented on threats to Singapore and Malaya from Indochina.
Britain employs home-raised, Indian, and Dominion troops against select French colonies that are typically the more strategically located, smaller, and vulnerable islands, straits, and chokepoints than others.
One of the bigger anti-French colonial tasks is the occupation/neutralization of French Indochina. Here the British are far from alone. Their forces only operate in and occupy the relatively small, but rich districts of Cochinchina including Saigon and the Mekong delta, while Siam is encouraged and supported in reclaiming its protectorates over Cambodia and Laos, and Japan, whose forces after the battle of Mukden are on track to march forth to occuoy the rest of Manchuria, the Russian maritime province, and Sakhalin while the Russians deal with quelling revolution, coastal defense, and central Asia, spare an expeditionary force to invade and occupy French Tonkin and Annam.
The British are pressing the Ottomans throughout the war to open the straits to them to permit attacks on the Russian Black Sea fleet and coast. While Abdul Hamid is pleased to be seeing Russia hurt in this war, he knows his own fleet and military forces are weak, and doesn't exactly trust the British.
He insists on guarantees for himself and the Ottoman Empire for committing anti-Russian warlike acts like opening the straits for combined naval assault on the Black Sea coast.
These guarantees include a guarantee of territorial expansion at Russian expense, at least to Kars, Ardahan, Adjaria - the old 1875 border, major debt write-offs, a subsidy, and most of all, allied troops to stiffen the OE's ground defenses.
The British, spreading their relatively small home Army far and wide against the French Empire, find the most feasible way to manage the Ottoman demand is by sending and hiring troops from India and Japan to reinforce the Ottomans through Mesopotamia to augment the Turks forffor an attack on the Russians in northwest Persia, and an advance on Baku.
....and that's how you end up with a joint Japanese-Ottoman offensive operation, against the Russians, that happens to be in the Middle East/Caucasus.
...
Here is a second way
2. Circa 1901 Germany accepts British alliance offers on British terms, which are focused in the first instance on protecting common (but mainly British) interests in China and Manchuria). Germany swallows its distate for 'pulling Britain's colonial chestnuts out of the fire' for nailing down Britain as an adjunct to the Triple Alliance powers and encouraging it to avoid compromise, Ententes or alliances with the other guys, France or Russia.
Japan tilts itself toward this Anglo-German preponderance of power in the Far East, Japan wants open trade, and it competes in lower end market niches than Britain and Germany who, focused on higher quality goods, do not fear the Japanese in their sectors of the market. Additionally, the Russians are too arrogant and complacent about the Japanese to either commit to sharing Manchuria or to keep their hands off Korea.
Japan is an active consumer of British naval goods and training, but still does not get a vital element it got in OTL, a bilateral alliance treaty with with Britain. Britain is completely satisfied its Far East, global and European interests are ensure by its own strength and the strength of Germany and its Triple Alliance partners.
The knock-on consequences in Europe is there is no Entente Cordiale, no Morocco Crisis (as we knew it), Morocco's independence is maintained longer, and if divided into spheres of influence, Germany ultimately gets a share along the countries Atlantic coast, and no Anglo-Russian Entente.
Japan still finds Russian forward policy in northeast Asia intolerable, but hesitates to act against Russia in 1904, despite the impending completion of the Trans-Siberian railway, because lacking a signed alliance commitment from Britain to handle any additional enemies, it fears that Russia could call in effective French naval aid against Japan in a conflict. Russia strengthens its hold over Manchuria,with Japan barely keeping in the game, while Russia grows as a player in Korea and alternative patron that anti-Japanese Koreans can use.
In 1908, the Young Turk revolution occurs in the Ottoman Empire, and the new regime calls for delegates from all nominally Ottoman lands, even those where foreigners actually rule, like Austrian-controlled Bosnia-Hercegovina. This causes a crisis of legitimacy for the Austrian regime in Bosnia.
As a result, the Austro-Hungarian government feels compelled to annex Bosnia-Hercegovina. Unlike OTL, Britain doesn't complain, because of its favorable dispositions to the Triple Alliance powers in the ATL. The Ottomans, while upset, are bought off with a payment, and retrocession of the Sanjak of Novi Pazar. But the Serbs and Russians are inconsolable, demanding an Austrian reversal of the annexation, or failing that, compensation at Ottoman expense. (Berlin and Vienna make sure to share the compensation proposal with Istambul, where it is not appreciated, and prevents any chance of the Turks making a united front with the Serbs or Russians over the Bosnian issue).
Austria-Hungary is unable/unwilling to back down, and Serbia and Russia with a full mobilization on Austria''s borders designed to intimidate or impoverish her or both. Vienna begs for German, Italian, and British solidarity.
While the Italians are noncommittal, the Germans prepare a demarche demanding the Russians stand down and get the Russians to stand down. The British want the Russians to stand down, although not eager for a wide war. They express understanding and support for what the Germans feel have to do. They do not promise to make war on the Russians or French, [but promise to make no promises to *not* fight them] but promise to keep the sea lanes to Germany open, remind the French that their violation of Belgian neutrality would be a casus belli, and invoke the principles of the Berlin Congress on Africa that signatories agreed that European Wars should not be taken into Africa, as a measure to protect particularly vulnerable German African colonies like Togo and Kamerun from French assault.
This Russian generated casus belli and British diplomacy encourages Germany to ultimatum the Russians before their mobilization is complete, and should that fail to convince, attack east with the Austrians, while defending in the west if the French choose to enter the fray.
The Russians press their luck too far and that is exactly what ends up happening.
The 1908 and 1909 campaigns are consumed by German and Austrian campaigns against Russian Poland and Lithuania and Serbia, German defense in Alsace-Lorraine, and limited Franco-German naval duels on the high seas.
However, in early 1909, Japan opportunistically attacks the Russians at Port Arthur and its legation forces in Korea seeing it and its French ally fully engaged. Likewise, the Ottoman Empire makes an alliance with Germany and declares war on Russia.
This unreformed Russian army, having never learned lessons of the Russo-Japanese war, is being beaten fast by Germany, unable to respond well in the Far East and Caucasus, and unable to successfully absorb new loyal recruits while handling revolutionary unrest, leading to the overthrow of the Tsar no later than early 1910, further fragmentation on national and ideological lines.
With Russian formal resistance ending, replaced by a revolutionary regime, and revolutionary chaos, France stops wasting itself on futile offensives into Germany. The powers that had been fighting Russia Germany, Austria, Turkey, Japan, eventually Romania and Persia - not formally neutral Britain, stay involved involved in Russia under a new rationale, restoring 'order' in strategic buffer areas and propping up 'buffer states' often demographically dominated by ethnonational minorities.
The British themselves may eventually get involved.
In the Far East, the Japanese lead a coalition of forces that includes Korean (remember, not yet annexed by anyone), Chinese and Mongol troops that crosses over the Russian border that fights revolutionaries, protects Asian merchants and to one degree or another contests various Russian territorial gainst of the last half century.
With the dramatic crumbling of Russian military power, the Japanese, with some some German and possibly British funding, and possibly augmented by German colonial Askari troops from Tanganyika, provided some bat Diivisions to augment Ottoman advances into the Caucasus and Turkmenistan.
....so that's how you get joint Japanese-Ottoman operations in a scenario.
