Taxation of Belgium military and NATO pensions in the United States for US resident

My reading of the NATO treaty and the tax treaty between the US and Belgium leads me to the following conclusions. I will assume your client is a resident alien of the US but not a US national.

1. Assuming that the military pension is a government pension (can't see how it would be a private pension), it is only taxable by Belgium per Article 18(2). However, it it turns out that your client is also a US national then it is taxable by the US.
2. There is nothing in the NATO treaty that excludes from income tax a NATO pension paid to a US resident or citizen. If we are discussing the pension scheme that currently has the employer contributing 12% of wages and the employee contributing 8% of wages, then it is taxable by the US. Please note that under the NATO treaty employees of NATO are not subject to Belgium income tax on their wages. Neither are foreign military assigned to NATO subject to Belgium income tax. As no US tax was ever paid on the wages, the whole pension is taxable by the US.

To sum up:

The US - Belgium treaty states that the US can not tax a government pension sourced from Belgium for services to Belgium unless the person is both a US resident and US national.

The savings clause in the US - Belgium treaty is not applicable to Article 18.

The NATO pension is not considered by the US to be social security and is subject to US income tax if the client is either a US resident or a US citizen.