Californian opinion was somewhat split before the outbreak of what had become called the "Second World War", retconning the Great War to be the "First World War". Before the war, many people had openly supported the fascists who held power in Germany, and a small but vocal fascist party known as "Calafia's Warriors" had gained enough traction to elect a single representative to the Congress in 1938. When the war broke out, however, public opinion began to sway heavily against fascism and Germany, to the point where even speaking German elicited suspicion. Opinion also heavily grew more and more anti-Japanese, with reprisals against Japanese citizens growing more and more common. Lynchings of Japanese-Californians grew more common as 1940 started. The government openly called for peace, but many in the administration began making plans for large-scale operations in the event of war.
In mid-1940, an emergency meeting of the North American League convened after the fall of France, which left Britain as the only force fighting against Nazi Germany in Europe. Prime Minister Alan Winchester of Cascadia and Prime Minister William King of Canada openly and loudly declared that the NAL should go to war against Germany, but President Garner of the CSA and President Roosevelt of the USA countered that a state of neutrality should be maintained. When Cascadia and Canada threatened to withdraw from the NAL over its inaction, a compromise was reached where the nations of North America would provide military aid and supplies to the United Kingdom while officially maintaining neutrality. This lifeline would prove to be an incredibly crucial aspect of keeping the United Kingdom alive and fighting, preventing Nazi domination of the continent. California's main contribution to the program of "Lend-Lease" was to provide supplies to Australia and New Zealand, which were engaged in campaigns against the Imperial Japanese Navy in the eastern Pacific.
Then, the hammer came down.
Prior to the 22nd of June, 1941, the Empire of Japan had invaded and captured the Hawaiian Islands from the British, which had alarmed many in the Californian Armed Forces, who alerted President Warren that the capture of the islands gave Japanese naval forces the range needed to strike at the Pacific coast of North America. Many brushed this off, since California wasn't at war with Japan. However, Japan had been growing angrier and angrier with the North American League as sanction after sanction came down on them, especially after all oil exports to Japan ended in the aftermath of the Nanking Massacre.
On 22 June 1941, the same day that Nazi Germany began an invasion of the USSR, the Imperial Japanese Navy launched an attack on California. Two naval detachments launched an aerial attack on the cities of San Francisco and Los Angeles, the two largest cities in the nation and two of its largest ports. In the attack, the Gold House was directly struck by a bomb, and a stray bomb destroyed a portion of the main span of the Golden Gate Bridge, though it was kept from completely collapsing. In the attack, which was more of a move meant to inspire shock and terror rather than properly attack California, Vice President Goodwin Knight was killed, along with three members of the President's Cabinet, two Senators, and four Representatives.
The next day, President Warren delivered a speech on the steps of the damaged Gold House, giving what is considered by many to be the greatest speech in Californian history, which became known as the "Republic will Hold" address. In it, President Warren spoke firmly on the resolution of the California Republic in this time of crisis, and asked the Congress to issue a declaration of war. Two hours later, both houses of Congress voted overwhelmingly for war against the Empire of Japan. Rallying to the call, the North American League then convened and passed a resolution to go to war, bringing all of North America into war with the Empire of Japan. Three days later, Adolf Hitler declared war on the nations of North America. North America was at war.
In the opening days of California's involvement in the war, the War Department had only a few weeks to take stock of the situation of the situation of their military. The attack by the Japanese had heavily damaged civilian targets and industrial centers in the Bay Area and Los Angeles, as well as damaging military installations, but much of the hardware of war, that is, battleships, tanks, and planes, had been spared major damage, and most could be made ready after only a week or two of repair. Perhaps more critically, the oil refineries of Los Angeles, one of the most critical industries to fuel a war machine, were almost entirely untouched, and the actual oil fields that were further inland were completely out of the way of the attack. When the picture came together, the Japanese may have won the "battle" that was the 22nd Attack, but it was very much a pyrrhic victory. The whole of California's war machine had been dealt only minor damage. And this wasn't even counting the whole of the industrial base of North America, which stood behind California against the Japanese Empire. The War Department came to a single conclusion: Japan could be beaten with time and effort. The question was where to start.
As the main battleships and aircraft carriers were repaired and loaded for battle, Californian citizens began to flock to recruiting stations to volunteer for military service, swelling the military's ranks. Most notably, a large number of Japanese-Californian citizens volunteered, perhaps as a way of proving their loyalty to California in the face of their home country attacking them. Sadly, it wasn't enough to prove the loyalty of Japanese-Californians. Just months after the attack, the Homeland Safety and Security Act was passed into law, complimented by Executive Order 6033 from President Earl Warren. The declaration was simple, yet terrifying: Californians of Japanese descent were to be rounded up and removed from the coastal regions of California, with the justification being that if Japan invaded, they would collaborate with the Imperial Army and help bring down California. Naturally, a loud protest was raised by the Japanese-Californians, but the government remained resolute, and the deportations from the western states began as soon as August of 1941. However, the Japanese-Californian soldiers couldn't be deported, since every available man would be needed for the army. As such, the government decided to make one exception: any Japanese-Californian citizen who volunteered for service in the army would be exempt from internment. This only really applied to the men of the Japanese-Californians, however, and their women and children were taken to camps in Deseret and Arizona.
The first major operation of the war came in February of 1942, when a combined effort from the United Kingdom, USA, CSA, Californian, and Cascadian navies launched a massive operation against the Hawaiian Islands, to liberate them from Japanese occupation. The first wave failed dramatically, but through a massive push in the second wave, the island of Ni'ihau was seized, and through a campaign of "Island-Hopping", the Japanese forces were driven out of the islands bit by bit. The last of the Japanese forces, rather than surrender, committed ritual suicide. The scene was incredibly disturbing to the Allied forces, and it was a perfect indicator for the fight they were in for.
While American and Confederate forces fought alongside the British and Canadians in northern Africa in 1942, the Californians, who had become a sort of de facto leader of operations in the Pacific, devised a strategy in collaboration with the USA and CSA to go "island-hopping", a strategy of taking back islands one by one across the Pacific in order to bring the Home Islands of Japan into range of aircraft bombings. Another part of the strategy took into account Japan's industrial capacity. They had made the Imperial Japanese Navy into a formidable fighting force, but ultimately, they didn't have the ability to replace what they lost. Japan's army and navy were overstretched with their attempt to invade virtually all of Asia, and if they could keep pushing back hard against them for a prolonged period, Japan would crumble from the inside. Just like in Europe, it was going to be a war of attrition, but on the high seas of the largest ocean in the world.
In May 1942, the Californian navy ambushed two Japanese aircraft carriers, the Shōhō and the Hōshō, not far from the island of Midway. After a fierce fight, while California lost the destroyer Santa Cruz and sustained heavy damage to the battleship President Stafford, both Japanese carriers were sunk, and the path lay open to continue driving at the western Pacific. Ships from the whole of the North American League participated in an almighty battle at the island of Midway in July of 1942, and resulted in a decisive victory for the Allied Forces. In one battle, five of Japan's biggest aircraft carriers were sunk, along with the loss of the battleship Musashi, one of the two largest battleships in the entire Japanese fleet. At the same time, the Japanese lost thousands of their best soldiers and hundreds of aircraft, while the Allies lost just one smaller Union carrier and the Confederate heavy cruiser Stonewall Jackson. The Allied victory crippled the IJN, losing a large part of the Pacific from their effective control and opening the route to the home islands. Many considered the Battle of Midway to be the turning point of the whole Pacific War, and the day that Japan truly began to lose.
By mid 1943, Allied forces had pushed back through the Pacific as far west as the Solomon Islands, now working to relieve the threat of an invasion of Australia. As the allies in Europe prepared an invasion of France to open a second front to the war, the Japanese were in a constant state of retreat, fighting like mad to keep what they had before being forced to give it up and moving back to the next island. A daring effort from Californian and Union forces managed to achieve a small-scale bombing raid on the home islands of Japan, striking the industrial centers and naval bases in Tokyo and Osaka, but without causing enough damage to truly disrupt Japan's industrial capacity. The bombing raids were more achieved for propaganda, showing that the Japanese could be attacked where they lived. In 1943, a Japanese assault on Allied positions in Papua New Guinea failed miserably, further dampening the Japanese ability to fight back against the advancing Allied forces and ending any chance of invading Australia. A key part of the Allied ability to fight the Japanese effectively was the "Translation Committee" of the War Department, whose nominal job was to translate messages into Japanese to broadcast terms of surrender to Japanese commanders, but whose actual purpose lay with a group of men from Navajo who spoke the Navajo language fluently, and used it to create a code that the Japanese had no ability to translate. Many considered the "Navajo Code Talkers" to be among the men who saved the war.
On the home front, by 1943, California had gone into a state of "total war". Every aspect of the economy had gone from a peacetime consumer economy to using every available resource that wasn't necessary for the wider population as fuel for the war machine. With so many men on the frontlines, women had become the new largest source of labor for factories and businesses. The popular Union image of Rosie the Riveter had become a common symbol in North America to represent women working in factory jobs to supply the men at the front lines with everything they needed to win the war. And by 1943, victory had become more and more likely when compared with the seemingly impossible challenge of beating back the Empire of Japan back in 1941.
By 1944, the climax of the war was approaching. Great Britain, Canada, the United States, and the Confederate States had invaded Brittany and opened a second front in Europe. At the same time, the Japanese Empire was on the retreat on all fronts. Battles in the Mariana Islands, Guam, and Marcus Island had sent the IJN further and further back. As the first aerial raids began to burn Japan's homefront industry, a new question arose: the final stages of the Pacific War. This proved to be a major point of contention in the Election of 1944, where Progressive candidate Harold Godric called for an end to the conflict then and there, with Japan on the retreat and being hit with bombardments from above, while Bear Flag candidate Frank Merriam called for the full surrender of the Japanese Empire. While the election proved contentious, ultimately Merriam won the election, and became the 19th President of California. Merriam's government then announced to the Japanese government that there would be no negotiation, and the North American League would only accept an unconditional surrender.
It was at this time that in 1944, a breakthrough was made on what would prove to be the most influential device of the 20th century, superseding the car, the plane, the telephone, the radio, and the computer in its influence on the future history of the world. Across the North American League and in collaboration with the British Empire, the "Manhattan Project" had been working to create a device so powerful in its destruction that it could destroy an entire city in a single go. It was in 1944 that physicists at the University of Berkeley achieved the creation of a nuclear reactor, only the third to ever be made in the history of the world, at the same time that an enrichment procedure for uranium was perfected. Progress on the bomb was accelerating rapidly, even with the coordination between 7 nations.
In 1945, as the flag of the North American League was hoisted over the island of Iwo Jima and the Allied navies advanced on Okinawa, Nazi Germany surrendered. Europe was split in half: the east was occupied by the USSR, and the west was occupied by allied forces, with Germany in particular divided into zones of Soviet, French, British, and North American control. But Japan still persisted, with the government of the Empire split between asking for a conditional surrender and refusing surrender, even if it meant an invasion of the Home Islands. Bombing raids grew more common in the first half of 1945, softening up the Japanese defenses in preparation for the proposed "Operation Setting Sun", an invasion of the Home Islands. Wanting to avoid as many casualties as possible, the Manhattan Project sped up progress on the bomb, finally producing a working nuclear weapon that was detonated outside the town of Thoreau in Arizona, the first nuclear blast in human history. With the weapon proved to work properly, Operation Setting Sun was put on secondary priority, and the new plan to drop an atomic bomb on Japan under "Operation Candlelight" was brought to the forefront.
The final team selected to drop the bomb was composed of men selected from every nation taking part in the project. While California lost its bid to have the pilot be Californian, the NAL chose a Cascadian man to fly the plane. However, California did manage to have Michael Conagher selected as the man who would ultimately make the final preparations for the weapon to be dropped. Operation Candlelight went into motion on the 13th of August, 1945. A single Confederate bomber, the Mississippi Queen, took off from the Allied-held island of Okinawa, flying north to the Home Islands. While whatever air forces the Japanese had left were tied up in attempting to defend against the Soviet invasion of Manchuria, the Mississippi Queen was able to fly into Japanese airspace undisturbed. At 9:47 AM, history changed forever. While flying over the city of Nagasaki, the bomb was dropped. The bomb fell for 46 seconds before exploding in the largest man-made explosion in history. In less than 5 seconds, more than 70% of the city was destroyed, and more than 50,000 people were killed either instantly by the blast itself, or by the shockwave. The resultant firestorm immolated many more, and tens of thousands more were injured. When looking back at the cloud, Conagher, knowing he'd made the bomb ready to go, uttered a single sentence that went down in history.
"My God. What have I done?"
Three days later, another bomb was dropped on Kokura, killing another 70,000. Two days after that, a third bomb was dropped on the city of Hiroshima, killing yet another 85,000 people. The very next day, the Japanese Government agreed to a total, unconditional surrender. After 6 years of slaughter, the greatest, most destructive conflict in the history of the human race was over.