According to a study by the Brown University-affiliated Watson Institute, the war in Iraq, which former Defense Secretary Donald Rumsfeld said would last less than six months, may cost over $6 trillion over the next 40 years. Taxpayers will not be off the hook after 40 years, however.

According to an Associated Press investigation into disability and survivor benefits, we are still paying for conflicts dating back to the Civil War.

Here's what some historic wars are costing us, according to the AP:

The daughter of a Civil War veteran receives $876 a year. The second-to-last Civil War beneficiary died last year.

The Spanish-American War (1898) costs taxpayers a total of $50,000 annually for 10 beneficiaries.

World War I-related benefits for 2,289 recipients add up to $20 million a year.

Compensation linked to World War II peaked in 1991 and now totals $5 billion a year.

Benefits for Korean War vets and their families come in at $2.8 billion a year and appear to be leveling out.

Benefits tied to Vietnam are still rising annually—$22 billion a year at last count.

Benefits for veterans of the first Iraq war, the war in Afghanistan, and the second Iraq war cost $12 billion annually—not including medical care—and the cost is rising. Some 45 percent of Iraq and Afghanistan veterans have applied for disability benefits.

These figures come from four compensation programs that identify recipients by war. Other expenditures—such as the budgets of the 1,700 facilities the Department of Veterans Affairs operates across the country—are not easily broken down by conflict and are thus not included in the tally.

Just a little something to consider next time we decide to start a quick war.