From the American Revolution until World War II, presidents and lawmakers avoided long-term indebtedness to pay for military conflict.

1790

Alexander Hamilton and James Madison forge a compromise in which the federal government assumes the states' Revolutionary War debt.

1796

George Washington warns against saddling "future generations" with war debts.

1919

Major increase on personal and business income taxes covers about one-third of U.S. costs for World War I.

1941-1968

An era of massive, long-term military spending begins with the biggest military conflict in U.S. history and continues into the long Cold War.

1942

A year after the United States enters World War II, 5.4 million men are serving in the U.S. Army.

1945

The fifth of a series of war bond drives among the public raises $20.6 billion -- for an overall total of $87.3 billion. ... Wage and price controls and rationing hold down civilian spending. ... Wartime tax-code changes dramatically boost the number of taxpayers to 42 million, from 4 million before the war.

1951

With the Korean War under way, President Truman proposes a $10 billion tax increase and settles for $7.2 billion.

1968

The Tet Offensive by the North Vietnamese military fails but shocks U.S. public and politicians with its sweep and intensity. ... President Lyndon B. Johnson proposes 10 percent tax surcharge to help finance war, accepting $6 billion in cuts to social programs. ... U.S. forces in Vietnam expand to 536,000.

1990-2002

Iraq becomes a major U.S. military adversary under dictator Saddam Hussein.

1990

Saddam orders his military to seize neighboring Kuwait. ... President George H. W. Bush begins assembling an international military coalition to free Kuwait.

1991

After weeks of air bombardment, U.S.-led land forces expel Iraq in 100 hours of fighting. ... The United States provides the majority of troops and thus pays only $13 billion of the cost, while allies pay $48 billion.

2000

U.S. contingent enforcing United Nations sanctions against Iraq includes 30 Navy vessels, 175 airplanes and as many as 25,000 soldiers at a total cost of $16.4 billion.

2002

Following the Sept. 11, 2001, terrorist attacks, President Bush begins laying the groundwork for "regime change" in Iraq. ... The president's chief economic adviser estimates war costs at $100 billion to $200 billion and is replaced. ... The director of the Office of Management and Budget estimates cost at up to $60 billion.

2003

Assistant Defense Secretary Paul D. Wolfowitz predicts Iraq's oil revenues will finance reconstruction. ... Bush administration proposes $20.3 billion for Iraq reconstruction.

2006

Iraq spends only 23 percent of its annual reconstruction budget.

2007

Iraq's oil revenues rise to $41 billion, up from $31 billion in 2006.

2008

War costs rise to an expected $160 billion for the year, following year-by-year increases from $53 billion in 2003. ... An increase in foreclosures, the collapse of Bear Stearns and the rise in unemployment prompt growing concerns over economy. Economist Joseph E. Stiglitz and budget expert Linda J. Bilmes calculate the total eventual cost at $3 trillion.