The crisis in Crimea represents the most significant security threat on the European continent in decades, and poses a real threat to Ukrainian sovereignty and territorial integrity.
But in truth, it also poses wider questions about the resolve of the West in the face of a flagrant breach of international law on Europe’s doorstep.
Given the continuing potential for catastrophic misunderstanding or simply misjudgement on the ground, the priority remains de-escalation, with Russian troops in Crimea returning to their bases, and the start of a meaningful dialogue between the governments in Kiev and Moscow.
Even with these steps, this crisis risks dividing Ukraine along ethnic and geographic lines - as shown by the latest move towards a referendum on Crimea’s status, in violation of the Ukrainian constitution.
But as well as the immediate security threats to the Ukraine, Russia’s recent actions have also reaffirmed the existence of a geopolitical fault line that the West ignores at its peril.
So now, over a week after Russian troops took effective control of the Crimea, the West must raise the costs to Mr Putin for his reckless actions.
It was disappointing that the EU's unity in condemning Russia's military aggression has not so far been matched by a shared resolve to act more decisively.
EU leaders did agree to suspend negotiations with Russia on visa liberalisation and on deepening their trade and investment relationship.
On the critical issue of possible financial and economic sanctions, however, there is no commitment to act, the EU Council merely committed to 'take forward preparatory work’ on these measures.
The Council also failed to lay out any sort of deadline by which to make its next decision. Instead EU leaders simply noted the need for results “within a limited timeframe”
The lack of concrete measures will not have gone unnoticed as the Kremlin calculates its next moves.
And many this weekend will inevitably be asking whether the lack of a clear timetable reflects deft diplomacy or implicit disunity on what actions should be taken and when.
The right approach for Europe to pursue, along with our allies, is a twin-track strategy.
On the one hand, we must be clear that we want to see an inclusive government in Kiev, with protection for the rights of the Russian minorities within the Ukraine and guarantees that the EU Association Agreement does not preclude continuing trade relations between Ukraine and Russia.
On the other, Europe must be more explicit about the real costs and consequences for Russia if it fails to de-escalate this crisis.
Russia is now significantly more integrated into the world economy than it was at the time of the 2008 crisis in Georgia, let alone during the earlier era of Soviet expansionism. President Putin has also based much of his appeal within Russia upon the promise of rising prosperity.
Today the EU is Russia largest economic partner, with an annual trade £275bn, and the UK alone handles at least £2bn of Russian business in financial services a year.
So the EU should be prepared to implement a graduated hierarchy of diplomatic and economic measures that could help effectively pressure Russia into changing course.
First in coordination with our allies, we could suspend negotiations on Russia’s application to the OECD, a group dedicated to boosting economic growth amongst its 34 members.
Second, the most powerful means to alter the Kremlin’s course is to target those elites upon whom it relies for its support. So EU leaders should set a clear deadline for progress by Russia within the days ahead, after which its members will impose an EU-wide freeze on the assets of Russian officials suspected of involvement in the military actions against Ukraine.
Third, the serious concerns about corruption in Ukraine must also be acknowledged. According to Transparency International one in three Ukrainians report paying a bribe when dealing with public services. So while the EU has already frozen bank accounts of Ukrainian officials who have stolen billions of dollars from the treasury, those measures could be extended – as President Obama has already done - to Russian officials also responsible for misappropriating Ukrainian state funds.
Fourth, the G7 must go further than its current condemnation of Russia’s aggression. Unless rapid progress is made the G7 leaders should seek agreement to suspend Russia from the group until it changes course.
The Prime Minister has said that he believes all economic and diplomatic options should remain on the table, and the UK Government has Labour's support in this approach.
So the UK should continue to work to ensure that having divided Crimea from the rest of Ukraine militarily, Putin does not now manage to divide Europe from our American allies diplomatically.
As upholders of the international order - with a permanent seat on the UN Security council, the G8, and the EU - the United Kingdom, along with our allies, has responsibilities that extend beyond simply our bilateral relations with Russia.
This includes the responsibility to remind our European allies of the importance of upholding the principles and agreements upon which European security is based.
What EU leaders who oppose further specific economic and financial measures must understand, is that there will be real and lasting consequences for the West of not demonstrating resolve in the days and weeks ahead.
The consequences are clear: a Russia emboldened in its ambitions towards Ukraine; a central Europe fearful of future political destabilisation and military insecurity; and a United States increasingly concerned about Europe’s willingness to act, even diplomatically and economically, in the face of such threats.
The West will find itself weaker and not stronger in the face of further challenges if it fails to put forward a clear timetable for action and to state more explicitly the economic measures that it will take to encourage Russia to change course.
Because, whilst this crisis is loaded with echoes of the Cold War, it may not be from Moscow alone that the West faces such threats in future decades.
The first task is de-escalation. Important as telephone diplomacy is, shuttle diplomacy is also now needed given the continuing risks of conflict: US Secretary of State John Kerry should to travel to Moscow to explain face to face both the risks Russia runs and the routes still open to that de-escalation.
A combination of such deft diplomacy, shared resolve and a unified response are the best means by which we can de-escalate this dangerous crisis, and ultimately re-affirm Ukrainian sovereignty and preserve European security.
Douglas Alexander MP is Labour's Shadow Foreign Secretary
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