Threats of war are coming from a new alliance. Led by Russia and China this “Axis of Outcasts” also contains such troubled stakes as North Korea, Cuba, Iran, Sudan, Venezuela and anyone else who is an outcast in the international community. This is eerily similar to the 20th century coalitions that, in the two World Wars, were the enemy (that is, the side that lost). This 20th century axis of outcasts had at its core Germany and Austria, plus Turkey and Bulgaria during World War I and, during World War II Italy joined what was called the “Axis” along with Japan and several smaller nations. Turkey wisely decided to sit out World War II and what was left of the Austrian Empire was absorbed into Germany before the war began.
Then as now, the axis began with a vibrant new economic superpower (Germany then, China now) looking for more respect, territory and a “place in the sun.” The 20th century axis also had a declining empire (Austria-Hungary) playing the part of the hapless sidekick during World War I while Italy assumed that role in World War II. These days the loser sidekick is Russia, an empire no more but still eager to recapture past glories at any cost.
Russia has more power to start wars because Russia's center of power is far from China's center of power, so Russia can act independently without risking defeats that will affect China that much, unlike Italy's adventures that drew German power to save them.
And the nukes, of course.
Strategypage also notes something else I've mentioned. The wars in the world became "world wars" because different regional struggles had overlapping players in overlapping time frames, allowing us to lump them all together.
Nobody really intends to start a world war. That's risky and bloody.
But once all those regional struggles get going, the history types get to link them into a grander struggle. They'd be especially risky for Russia and China, as the Strategypage post notes.
I wonder if a Russo-China War is the only way to preclude a world war as China and Russia push neighbors and risk short and glorious wars that escalate out of hand?