In western Poland, U.S. troops and tanks areparticipating in military drills. They're part of a forceof 4,000 American servicemen and women who weredeployed to Eastern Europe earlier this month. It'sthe biggest U.S. military buildup in the region sincethe Cold War and Russia has spoken out against it.It sees the exercises as a threat to its borders.
It's not just U.S. troops who are involved. It's other members of NATO. And though theAmerican forces were initially sent by former President Barack Obama, it appears their workthere has the support of President Donald Trump. That's significant because he's repeatedlyquestioned the U.S. role in NATO.
According to the U.S. Army's lead commander in Europe, though, President Trump hasreassured several other NATO members that the U.S. remains committed to the organization.
NIC ROBERTSON, CNN SENIOR DIPLOMATIC EDITOR: What is NATO? Why is itimportant? And what's its future?
The North Atlantic Treaty Organization is a political and military alliance established in 1949that seeks to promote stability in the North Atlantic area.
UNIDENTIFIED MALE: It is a will of the people of the world for our freedom and for ourpeace.
ROBINSON: Led by Secretary General Jens Stoltenberg, there are 28 member countries and itsHQ is in Brussels.
NATO doesn't have his own troops but relies on contributions of forces from its membercountries. At NATO's core is Article 5 which states an attack on one member is an attack on allNATO allies.
The collective defense principle was to protect Western European nations against the SovietUnion. But when the Soviet Union collapsed, NATO's new tasks range from being a bulwarkagainst al-Qaeda in Afghanistan to fighting human trafficking and intercepting refugees in theMediterranean.
Donald Trump has called it obsolete, says it has problems.
DONALD TRUMP, PRESIDENT OF THE UNITED STATES: NATO is obsolete.
ROBERTSON: He thinks NATO's original purpose of protecting against the Soviet Unionmakes it irrelevant, that it's ill-equipped to tackle terrorism and that other members don't paytheir share towards it.
NATO is still extremely active with some 4,000 U.S. troops in Poland and the Baltic States, andtens of thousands on 48-hour standby — bolstering NATO's allies and sending a clear messageto Russia.
But the organization's future and its principle of collective defense could be jeopardized ifTrump pulls the U.S. out. Some of his cabinet picks back NATO, though, like General James"Mad Dog" Mattis, chosen to head the Pentagon, have categorically declared NATO necessary tothe USA.