Defending the US dollar by force

There is lots of stuff on the internet about the Iraq being attacked because the US wanted to make sure that Iraq continued to accept the US dollar. There are also stories about Iran being targeted next for the same reason (http://globalresearch.ca/articles/CLA410A.html). Before dismissing these claims as mere conspiracy theories, it might be well to consider that there is a historical precedence. I came across the following quote in The Middle East, by Bernard Lewis.

In 694 CE, Abd al-Malik issued a new caliphal gold coinage, with far-reaching implications and effects. . .The minting of gold coins had been a Byzantine prerogative, inherited from the Roman emperors, and there wore no other gold coins in the world. . . The Arabs had continued to import gold coins from Byzantium. Abd al-Malik's gold dinars - the name is of course adapted from the Roman denarius - were rightly seen as a challenge by the Byzantine emperor, who went to war in protest.