President Donald Trump's visit to the NATO summit on Wednesday is being closely watched for one big reason: will he commit ...

THE HAGUE, Netherlands — President Donald Trump on Wednesday once again raised questions about America’s commitment to defend ...

But NATO allies have also taken collective defense measures, including joining the U.S. to fight the Islamic State group in Syria, Iraq and Afghanistan as well as help keep the peace in the Balkans.

Article 5 is at the heart of the 31-member North Atlantic Treaty Organization. It states that an armed attack against one or more of the members shall be considered an attack against all members.

But if Ukraine joins NATO in the middle of the war, then Russia is at war with the entire NATO alliance. At the core of this conundrum is Article 5 - NATO’s common defense guarantee under which ...