Bonds were set to begin the day in fairly unchanged territory when Trump tweeted about launching missiles at Syria and forcing Russia to try to shoot them down (here).  That was initially of some benefit to bonds just before the start of the domestic session, but it didn't create any lasting momentum.  After all, bonds still had to get through all of the events that would surely cause bigger movement: CPI data, 10yr Treasury Auction, and the Fed Minutes.

But none of the remaining events really moved the needle.  CPI came in just a hair weaker, but was only weak enough to be traded as such by the time investors scoured the internals (thereby seeing medical supplies and "shelter" costs buoying the otherwise weaker price movement).  The 10yr auction was inoffensive, and the FOMC Minutes contained no new news.

With bonds in stronger shape than traders thought necessary in the morning, the day was spent gradually drifting higher in yield until the 10yr auction.  After the auction confirmed yields didn't need to go any higher, the rest of the day was spent drifting sideways to slightly stronger.