The cease-fire was always a joke between the two sides, the Russians/seperatists still launched large artillery strikes and carried out attacks. The only difference this time is that they launched a major attack on Donetsk airport, and the Ukrainians reinforced there defenses, the Ukranians tried a little harder to abide by it, but the Russians aren't playing ball, so were back to this. A Russian spring/summer offensive may be very likely as well, involving a lot more Russian regulars.