In the end, the leaders cobbled together a three-pronged compromise. In a first step, they announced the immediate halt of talks on easing visas for Russians and on forging a new economic agreement.
If Russia fails to enter negotiations with Ukraine that produce results "within a limited timeframe", additional punishments will be applied including travel bans, assets freezes and the cancellation of an EU-Russia summit, a statement said.
It added that any move by Russia to destabilise the situation in Ukraine would lead to severe and far-reaching consequences, including economic ties.
In decisions also bearing Poland's hallmarks, the EU has earmarked 11 billion ($18 billion) in support for Ukraine's tottering economy and declared it will sign a highly regarded "association agreement" with its caretaker Government even before the holding of elections in May.
Poland's place at the top table owes much to its status as one of the EU's stories of economic success.
The past 25 years have seen it switch from a smokestack economy based on mining, steel and shipbuilding to one of electronics and cars. Its GDP has doubled in this time and exports have risen by a factor of 20, from US$10 billion ($12 billion) in 1989 to US$200 billion in 2012, according to official figures.
The country is governed by conservatives who nurture bitter memories of the secret pact between Stalin and Hitler to divide Poland in 1939 and the country's post-war absorption into the Soviet empire, ending in the "annus mirabilis" of 1989.
For more than six years, Prime Minister Donald Tusk has been quietly nurturing relationships with other EU countries in central and eastern Europe, and piecing together a loose alliance with three other nations with similarly scarred pasts - the Czech Republic, Hungary and Slovakia - into what is known as the Visegrad Group.
In a joint statement issued in Warsaw this week, the Visegrad quartet members blasted Moscow. Its leaders said they were "shocked to witness a military intervention in 21st-century Europe that resembles their own experiences in 1956, 1968 and 1981", the dates of Soviet crackdowns in their countries.
At the centre of Tusk's foreign policy vision is securing a bulwark against Moscow, and within it is the priority of anchoring Ukraine with the EU and Nato. Ukraine and Poland share a 500km-long border and a common perception of history, of bouts of blood-stained Russian and German oppression. "There is no secure Poland without a stable Ukraine," Tusk has said.
Events today bear out predictions that the EU's centre of political gravity would shift to the east as a result of the "Big Bang" of 2004 when 10 countries, eight of them former communist nations of central and eastern Europe, joined the club.
The change is not without critics, though. Mention Poland in Brussels, and many will wince, recalling long hours of wrangling over the EU budget or political reforms when Polish representatives relentlessly demanded an ever-greater share of the European pie.
Roderick Parkes of the think-tank Polish Institute of International Affairs in Warsaw said Poland risked overplaying its hand in Brussels and might be better advised to use its economic clout in the east. "There's a sense Poland may be too dominant in this part of the world," he told the Weekend Herald. "What Poland perhaps needs to concentrate on now is to act as a model to the east, providing aid and investment."
