FILE - In this Sept. 5, 2014, file photo U.S. President Barack Obama looks around during a flypast at the NATO summit in Newport, Wales. Obama will begin this week to lay out a strategy to defeat Islamic State militants in the Middle East, starting with a White House meeting with bipartisan congressional leaders on Tuesday, Sept. 9, 2014 and a speech on Wednesday, the eve of the 13th anniversary of the deadliest terrorist attack on U.S. soil. (AP Photo/Jon Super, File)
FILE - In this Aug. 28, 2014 file photo, President Barack Obama speaks in the James Brady Press Briefing Room of the White House in Washington, before convening a meeting with his national security team on the militant threat in Syria and Iraq. The U.S. and its allies are trying to hammer out a coalition to push back the Islamic State group in Iraq. But any serious attempt to destroy the militants or even seriously degrade their capabilities means targeting their infrastructure in Syria. That, however, is far more complicated. If it launches airstrikes against the group in Syria, the U.S. runs the risk of unintentionally strengthening the hand of President Bashar Assad, whose removal the West has actively sought the past three years. Uprooting the Islamic State, which has seized swaths of territory in both Syria and Iraq, would potentially open the way for the Syrian army to fill the vacuum. (AP Photo/Evan Vucci, File)
U.S. President Barack Obama, right, points as he stands alongside British Prime Minister David Cameron, centre, and NATO Secretary General Anders Fogh Rasmussen during a flypast at the NATO summit at the Celtic Manor Resort in Newport, Wales on Friday, Sept. 5, 2014. (AP Photo/Jon Super)
alliance: U.S. President Barack Obama and Ukraine President Petro Poroshenko at the NATO summit at Celtic Manor in Newport, Wales, where they and other world leaders discussed Russian aggression. (Associated Press)
Both President Obama and British Prime Minister David Cameron (right) have stepped up their rhetoric on the Islamic State group this week, and are hoping to rally international support for defeating the terrorist organization while attending the NATO summit. (Associated Press)
U.S. President Barack Obama, center, waves as he arrives for a group photo during a NATO summit at the Celtic Manor Resort in Newport, Wales on Thursday, Sept. 4, 2014. In a two-day meeting leaders will discuss, among other issues, the situation in Ukraine and Afghanistan. (AP Photo/Jon Super)
British Prime Minister David Cameron looks out from a top balcony at the Lodge as he waits for a television interview on the sidelines of a NATO summit at the Celtic Manor Resort in Newport, Wales on Thursday, Sept. 4, 2014. In a two-day summit leaders will discuss, among other issues, the situation in Ukraine and Afghanistan. (AP Photo/Virginia Mayo)
Houston Texans defensive end J.J. Watt, center, celebrates his sack with teammates Jadeveon Clowney (90) and Jerrell Powe (95) during the first half of an NFL preseason football game against the Arizona Cardinals, Saturday, Aug. 9, 2014, in Glendale, Ariz. (AP Photo/Matt York)
President Obama spoke in Estonia about the need for NATO to defend its member states, many of whom are wary of Russian incursions similar to what has occurred in the Ukrainian theater. (Associated Press)
A statue of Confederate Gen. Thomas "Stonewall" Jackson stands at Manassas National Battlefield Park at Manassas, Virginia. The park offers three hiking trails of varying lengths, a ranger-led walking tour and a network of roads that allows for self-guided driving tours. (Associated Press photographs)
A view of Burnside Bridge and Antietam Creek at Antietam National Battlefield in Sharpsburg, Maryland. Among the superstitious, Antietam is considered to be the most haunted of the Civil War battlegrounds.
Manassas National Battlefield Park also houses a visitor center and two historic structures, including the Brawner Farm Interpretive Center, an accurate replica of the farmhouse originally on the battlefield.