With US forces operating in Syria on anti Isis missions. I take it this mission is backed by NATO. So if their forces are attacked by other national groups would that entitle the US to trigger article 5.
The US Forces inside Syria may not be backed by NATO. Their deployment looks like a unilateral decision. Article 5 states:
Article 5
“The Parties agree that an armed attack against one or more of them in Europe or North America shall be considered an attack against them all and consequently they agree that, if such an armed attack occurs, each of them, in exercise of the right of individual or collective self-defence recognized by Article 51 of the Charter of the United Nations, will assist the Party or Parties so attacked by taking forthwith, individually and in concert with the other Parties, such action as it deems necessary, including the use of armed force, to restore and maintain the security of the North Atlantic area.
Any such armed attack and all measures taken as a result thereof shall immediately be reported to the Security Council. Such measures shall be terminated when the Security Council has taken the measures necessary to restore and maintain international peace and security.”
Therefore upon the face of it, any attack on US Forces in Syria by Russian Forces would not trigger Article 5. However Article 6 states:
Article 6
“For the purpose of Article 5, an armed attack on one or more of the Parties is deemed to include an armed attack:
- on the territory of any of the Parties in Europe or North America, on the Algerian Departments of France 2, on the territory of or on the Islands under the jurisdiction of any of the Parties in the North Atlantic area north of the Tropic of Cancer;
- on the forces, vessels, or aircraft of any of the Parties, when in or over these territories or any other area in Europe in which occupation forces of any of the Parties were stationed on the date when the Treaty entered into force or the Mediterranean Sea or the North Atlantic area north of the Tropic of Cancer.”
- Article 6 has been modified by Article 2 of the Protocol to the North Atlantic Treaty on the Accession of Greece and Turkey.
- On January 16, 1963, the North Atlantic Council modified this Treaty in its decision C-R(63)2, point V, on the independence of the Algerian departments of France.
- Documents on Canadian External Relations, Vol. 15, Ch. IV.
Source:
Collective defence - Article 5
The
Economist states that:
Much NATO effort is now going into ensuring that it can respond in a practical way, militarily and politically, to appeals for help. All the strength of the world's mightiest military alliance will not amount to much if its members cannot agree when an aggressor has actually stepped over the line. (My emphasis)
This appears to mean that if the US invokes Chapter 5 in Syria, then NATO may not respond as the US would like because of possible disagreement amongst member nations about the response. Whilst NATO agreed to combat terrorism, it could be argued by some that once Daesh is defeated in Syria and Assad reestablishes full control over the Syrian nation, the US has no grounds to stay within Syria especially as it wasn't invited in by the Syrian government.
That's my take on it.