As an amateur with a hobby in foreign affairs, I can say the following based on reading many experts for years but with no expertise of of my own:

> Or is just about using military might as a political & diplomatic tool?

Military might is always a political tool. One of the most famous, enduring descriptions of war, by arguably its leading theorist, 19th century Prussian General Carl von Clausewitz, is 'the continuation of politics by other means'.

Sometimes you threaten with your military power, sometimes you fight, but either way it's always for political reasons. Nations pursue war to obtain political goals and wars end with political settlements. Sometimes those settlements are vastly unbalanced, such as total surrender, but they're still political - 'we agree that you will govern us' - otherwise you keep fighting. When nations forget that then they waste blood and treasure - look at the U.S. invasion of Iraq, which lacked a political aim and thus found itself in a quagmire after the military goal, the overthrow of Hussein, was achieved. That lack of political resolution left a political vacuum which persists to this day, and which ISIL, Iran, the Kurds, and others have tried to take advantage of; the wars there will end when there is a stable political equilibrium.

> Do they believe there is a realistic chance of war with these countries?

RUSSIA is mostly bluster but they do have some capability; they are a threat to small, poor neighbors; and of course they have nuclear weapons. They can cause pain but would be absolutely insane to fight a real war with NATO (though that hasn't stopped some people). Their current strategy is to approach the line but not cross it; e.g., occupy neighboring parts of Ukraine and Georgia but stay away from NATO borders.

The foundation of military power is economic power; money buys more and better weapons (and friends too). Russia can't possibly afford to compete with NATO; they can't really afford their current operations, which are on the cheap (the Ukrainian province of Crimea was conquered with a small number special operations soldiers, for example). Annual economic output (GDP) of NATO, Russia, and selected countries says it all:

* NATO: $37 trillion

* U.S.: $17 trillion

* Germany: $3.9 trillion

* UK: $2.9 trillion

* Canada: $1.8 trillion

* Russia: $1.1 trillion (with a shrinking population and also a shrinking economy based on mineral wealth, not technology or industry)

CHINA is a much more serious issue. Remember the economic foundation of military power. China's economic output likely will surpass the U.S.'s in the next decade. With four times the U.S.'s population, it's not crazy to imagine China's economy being twice the size of the U.S.'s in future decades. Then what happens?

Much history has been studied and written about what happens when a rising power overtakes the existing dominant power. The result usually is war. Like an old incumbent tech company, the old dominant power can't see their obvious situation and tries to hold on to their historical position; the rising power refuses to remain subordinate.

The last time it happened, in the late 19th and early 20th centuries, the U.S. was the rising power and the European powers were the incumbents. To the Europeans the U.S. was about as benign as they could hope for: A relatively peaceful democracy, sharing the same values and culture, filled with European immigrants, and a great trade partner who enriched them all. Broadly speaking, they accommodated the rise of the U.S.; by the end of WWII, with Europe devastated by two massive wars, the transition was complete. According to one account I read, during one international security crisis in the 50s (Suez?) the UK government actually called the US and said, effectively, 'we can't handle this any more, it's your job now'. The U.S. has been primarily responsible for global order ever since.

China seems much less benign, a dictatorship that is openly threatening everyone from its neighbors to the U.S. to European nations. Many nations view the U.S. as a relatively very benign hegemon, actively seeking alliances and U.S. forces based in their countries. Another common pattern when a new power arises is that the others ally against them as a balance. Right now that seems to be happening around China, with Japan, Vietnam, the Philippines, Australia, India, S. Korea and others busily forming stronger bonds with the U.S. and among themselves in response to China's bellicosity.

But it's a very long game, one that will last a generation or more, so nobody knows.