Russia Ukraine
Honor guards of the self-proclaimed Donetsk People's Republic attend a ceremony at the memorial of Russian revolutionary Fyodor Sergeyev, known as Comrade Artyom, in Donetsk on Nov. 14, 2014. U.S. President Barack Obama described Russia's aggression against Ukraine as "appalling" at the G-20 summit. Getty Images

When American, Russian and British leaders came together to sign the Budapest Memorandum in 1994, ensuring the territorial integrity and political independence of Ukraine, few thought that exactly 20 years later to the day Russian troops would be operating in East Ukraine and Crimea, seemingly flouting the agreement.

The anniversary of the memorandum falls on the same day that Ukrainian President Petro Poroshenko urged Ukrainian troops not to lose control of the Donetsk airport, fearing that the entire Ukraine will be in danger if the airport falls into the hands of the “enemy" -- pro-Russian separatists in the east of the country, backed by troops and equipment from Moscow.

The agreement was first broken when the Kremlin intervened militarily in Crimea in February of this year, when troops with no insignia appeared on the streets. The military takeover led to the eventual annexation of the peninsula by Russia, after a referendum that was rejected as illegitimate by the international community.

At the time, Russia denied that the unmarked troops belonged to its military or were under Russian command. By April, similar scenes began to unfold in Donetsk and Luhansk in eastern Ukraine, where separatists declared independent entities that were not recognized internationally and fought the Ukrainian government's troops. The international community accused Russia of orchestrating the separatists' military moves and alleged that Russia was trying to create a "frozen conflict" designed to stop Ukraine from joining NATO and the EU.

By September, NATO satellite evidence showed Russian armor crossing the border into Ukraine, which brought the memorandum into question once more. But as the troop loads and weapons continue to flow into the country and 150,000 Russian troops are stationed on the Russian border with Ukraine, Russia may no longer be bothering to hide the fact that it had violated the agreement.

However, there appears to be little recourse to enforce article one and article two of the memorandum, which is not an international treaty. The text states that the signatories of the memorandum must “respect the independence and sovereignty and the existing borders of Ukraine” and “Refrain from the threat or use of force against the territorial integrity or political independence of Ukraine.”

According to NATO, those pledges have now clearly been broken. European Union and U.S. sanctions have not stopped Russia from action in East Ukraine, which included uniformed Russian troops crossing the border in military columns carrying heavy-duty weapons.

Steven Pifer, a senior fellow at the Brookings Institute and director of the group's Arms Control initiative, wrote that “Washington should do more.” Namely, “It is time to provide the Ukrainian military defensive arms, such as light anti-tank weapons. That would raise the costs to the Russian army of any further fighting and help deter it."