As outlined a short time ago on Checkpoint, the cost of the U.S. military campaign against the Islamic State is likely closing in on $1 billion, and could rise at a cost of between $200 million and $320 million per month as it continues.

This graphic was produced by colleagues at The Washington Post with information released by U.S. Central Command and compiled in this spreadsheet I posted on Google Docs. It shows that the pace of U.S.-led airstrikes in Iraq and Syria have increased rapidly, especially since President Obama called for the first ones in Syria on Sept. 23. In the span of less than a week, there had been 51 there as of early Monday afternoon. Twenty-eight more have conducted in Iraq in that timeframe.

A caveat: Airstrikes in Syria are being conducted with five other Arab partners: the United Arab Emirates, Jordan, Saudi Arabia, Bahrain and Qatar. Qatar has been flying support missions, while the other four have been dropping bombs, U.S. officials say.

In Iraq, the bulk of the airstrikes have been carried out by the United States, but the Iraqi military and France also have dropped bombs, and other nations, including Britain, have pledged to join the campaign soon.

U.S. bombs have been dropped by aircraft flown by the Air Force, Navy and Marine Corps.