"China is going to invade the mainland. Japan will be absolutely fine in the event of an actual exchange of fire. So will Taiwan. Russia will protect all its capital cities against invasions. No matter what, they will emerge from any hypothetical conflict unscathed.

In contrast, Russia’s military infrastructure in Syria is meant to deter future NATO efforts to bring down a pro-Russian government in the Middle East. Russian aid to pro-government rebels includes protecting them from ISIL.

Such an effort is worth at least as much to Moscow as it would be to Washington to get NATO involved in Syria.

This obviously threatens the security of Americans, but we are also entering uncharted waters. The Chinese government could be toppled, and the US military could seize Chinese assets as part of the war. China could also use its navy in the Pacific to blockade shipping in and out of the United States, and could actually begin to build a blockade around the United States to prevent trade with its allies."

This is a significant problem, but it is not one for the United States to decide unilaterally

• Donald Trump