In a televised address Friday, President Obama announced that the U.S. would withdraw all U.S. forces from Iraq by year-end.

Gen. David Petraeus, former commander of Multi National Forces in Iraq, salutes Iraqi soldiers in 2008. (Warrick Page/Getty Images)

Troop levels in Iraq have fluctuated greatly since the U.S. invaded in 2003. The Federation of American Scientists, which has tracked these numbers throughout, reports that the decision to reduce troops in Iraq reflects “declining levels of violence” and confidence from January 2009’s “peacefully conducted” provincial elections. The decision, however, remains widely controversial.

Below, see a graph of how troop levels have fluctuated since the war began:

29: Number of Americans killed in Iraq in 2011, according to

486: Number of Americans who died in Iraq in 2003, the year the war began, according to

904: Number of Americans who died in Iraq in 2007, the year of the greatest number of casualties, according to

4,459: Total number of U.S. troops killed in Iraq, according to

100,000+: Estimated number of Iraqi civilian deaths, according to database Iraq Body Count.

And some of the numbers on the cost of war:

782 billion: Spent and approved dollars for war-spending in Iraq, according to research organization Cost of War.

9 billion: Dollars lost and unaccounted for in Iraq as of 2010, according to Russia Times.

500 billion: Cost of medical care and disability compensation dollars for Iraq war veterans over their lifetimes, according to the House Committee on Veterans Affairs.

3 trillion: Dollars of estimated total cost of the war. according to military news site Stars and Stripes.