Bond markets were already in positive territory to begin the day, thanks to news over the weekend of ongoing ballistic missile threats from North Korea.  Trading was fairly sideways at those stronger levels for the first half-hour.  This was fairly impressive in and of itself, considering several big corporate bond announcements between 8am and 830am ("little" companies like Apple, Home Depot, and Caterpillar).  For a refresher on the impact of corporate bond issuance, read this.

Then a Trump tweet came out at 8:36am, perfectly coinciding with the most recent leg down in bond yields:

"I am allowing Japan & South Korea to buy a substantially increased amount of highly sophisticated military equipment from the United States." -twitter

That brought 10yr yields more than 5bps lower to 2.113%.  Fannie 3.5 MBS are nearly a quarter point higher at 103-22.  Those are levels that put more and more focus on Fannie 3.0 MBS, currently up more than a quarter point at 101-07 (101.219).

There are no major economic reports set to come out today, but we will get some 2nd tier data at 9:45am and 10am (ISM New York and Factory Orders).  If the corporate issuance glut isn't inspiring bonds, we shouldn't expect the econ data to even have a chance. The bigger potential motivation will be the NYSE open in a few minutes, which could see its own glut of "new month" trading positions.  Although the NYSE is technically "the stock market," there are plenty of stocks that have a direct effect on bond trading (especially bond market ETFs).