Although both sides continued to trade sporadic artillery/rocket fire from 5 September on-wards, it was rebel actions in mid-January that killed Minsk. Those actions included a public rejection of the Minsk Agreement by rebel leader Alexander Zakharchenko who also announced a new multi-front offensive which initiated heavy fighting at the Donetsk Airport, heavy fighting around the rail junction of Debaltseve, and a rebel rocket attack on the city of Mariupol which killed 30 civilians and wounded over a hundred. Since the new rebel offensive began, rebels have acquired ~200 square miles of additional territory.
Pro-Russian rebels reject peace deal, launch new offensive
Regarding the US sending defensive lethal weapons to Ukraine, I now tend to think the
New York Times article of Feb. 1 breaking this story was a trial balloon by the Obama administration to gauge domestic and foreign reaction. Asked about arming Ukraine yesterday in his confirmation hearing before Congress, SecDef nominee Ashton Carter stated; "I very much incline in that direction ... because I think we need to support the Ukrainians in defending themselves." Clearly, such a statement would have been pre-vetted by the White House.
Which leads me to believe the decision has already been made. Looking at it pragmatically though, when it comes to Ukraine, Obama moves at a glacial pace. US Secretary of State John Kerry is scheduled to arrive in Kyiv today (2/5/15) for consultations.