The majority of the fighting took place in the Pacific and Asia; Europe remained calm (except for intensifying proxy wars) until the closing stages of the war.
The war saw the first large-scale conflicts in space, the most significant of these being a Chinese attempt to invade the US Lunar Territory.
The Great War was the deadliest conflict in human history. Its closing stages saw the rapidly-intensifying use of tactical nuclear weapons by both sides, primarily in China as Western forces sought a way to overcome Chinese numerical supriority. The strategic exchange itself later resulted in hundreds of millions of deaths, and the ensuing decade-long nuclear winter in many billions.
Prior to the 2050s, with the re-emergence of Russia and rise of China as superpowers, the world had again solidified into two primary (if loose) geopolitical blocs: the "western powers" centered around the US and European Commonwealth, and the "eastern powers" centered around Russia and China.
Rapidly growing instability in the Middle East and other regions of the world - a consequence of both climate change and attempts by the two blocs to exert their power - had by 2030 caused relations between the two blocs to deteriorate rapidly, paving the way for larger-scale conflict.
After peak oil was hit in the early 2020s, available supplies of fossil fuels began to rapidly dwindle; as a consequence, major powers moved to secure as much of the remaining supply as possible for their own national economies and to deny it to the rest of the world.
Fuel shortages began to cause modern agricultural methods to fail, resulting in an uptick in famine across the world, further contributing to political instability and displacement of populations.
The United States became increasingly authoritarian in order to suppress both opposition to the diverting of national resources to a massive military enlargement program (by 2047, the US Navy operated twenty carrier strike groups) and dissent caused by an economic downturn and growing domestic resource shortages.
Black Sea War
The Black Sea War lasted for three weeks in summer of 2020, and involved several cases of western and Russian units shooting at each other on the Ukrainian steppe. Unwilling to risk a large-scale escalation, western political leaders decided not to attempt to dislodge Russian forces from their positions in the south and east of Ukraine, instead opting to prevent any further Russian advances. The war concluded with the secession of southeastern Ukraine and the entry of western Ukraine into NATO.
Iran War and Arabian War
In 2026, following a period of escalating tensions and increasingly hawkish rhetoric, the United States initiated military action against Iran after the alleged sinking of two US guided missile destroyers by Iranian submarines in the Persian Gulf, an event which came to be known as the Persian Gulf Incident. The invasion of Iran greatly disturbed Russia, which had been trying to build a "Moscow-Tehran Axis"; two days after the US invasion got underway, Russian units took up positions in the north of the country. A tense diplomatic standoff ensued, which was resolved when Iran was divided into two - a US-backed "Republic of Iran" in the south and the Russian-backed Islamic Republic of Iran in the north.
Several years later, in a bid to secure the remaining oil reserves of the Arabian peninsula, a US-European coalition invaded Saudi Arabia after the national government had collapsed and fallen to Islamist rebels.
Second Korean War
In 2043, an error in several North Korean missile warning radars caused its leadership to believe that a western missile strike was underway, "retaliating" in turn with their own ballistic missiles at targets in South Korea and Japan. A swift joint US-Japanese-South Korean response saw the North Korean armed forces crippled by an air campaign, followed by an invasion of the country.
In May 2049, an engagement in the South China Sea resulted in the USS Lyndon B. Johnson (CV-89) sinking two Chinese coast guard vessels, in turn suffering superficial damage. As the carrier sailed towards her homeport of Yokosuka for repairs, she was hit by a Chinese anti-ship ballistic missile and, over the course of five hours, sank in shallow water in the Taiwan Strait on May 22nd.
In the early hours of May 23rd, a US Air Force stealth bomber squadron - at the time on airborne alert over the Yellow Sea - was ordered to attack the Chinese aircraft carrier Yunnan and her strike group in retaliation. Yunnan was hit by three anti-ship missiles, and by midday she had sunk alongside two guided missile destroyers and a supply ship. At the same time, a flight of stealth fighters based in Korea attacked the ballistic missile battery responsible for sinking USS Lyndon B. Johnson and inflicted severe damage.
A Chinese airborne retaliation on May 25th targeted Kunsan Air Base, which the fighters had launched from, with sea-launched cruise missiles and was successful in knocking it out of action and destroying its air wing.