Geopolitical risk is an old friend to bond markets.  When prospects for awful things flare up at home and abroad, money tends to flow out of stocks and into bonds.  That's been the case so far today as Treasury yields and stock prices have plunged in unison after a series of headlines out of Ukraine suggesting some semblance of civil war. 

Before that, bonds, including MBS, started out in weaker territory, but did a decent job of holding their ground.  Weaker-than-expected manufacturing data from the NY Fed may have helped to some extent as prices generally rose from there on out.

At present, bond markets continue delving into positive territory.  Treasuries are already well past yesterday's best levels and MBS are close to matching theirs.  There is no other significant scheduled data on tap, and its fair to assume that markets will remain on the lookout for additional Ukraine headlines.