A Ukraine soldier stands on a tank in a military camp near the eastern Ukrainian town of Rassypnoe on Aug. 25. Russia defied Western criticism by announcing that it will send a second aid convoy to areas in eastern Ukraine held by pro-Russian separatists. (Roman Pilipey/EPA)

As Ukraine looks increasingly under threat of a full-scale invasion, Ukrainian Prime Minister Arseniy Yatsenyuk suggested a remarkable defense plan: A wall along its border with Russia.

Speaking at a government session Wednesday, Yatsenyuk listed the potentially huge construction project "the Wall" among other defense initiatives. "It means constructing a real state border infrastructure between Ukraine and the Russian Federation,” Yatsenyuk said on his English-language Twitter account.

The concept of a physical wall between Ukraine and Russia was first mooted by Igor Kolomoisky, Ukrainian billionaire and governor of the Dnipropetrovsk region, back in June. While Yatsenyuk did not specify details Wednesday, Interfax reports that Kolomoisky's initial plan involved a 1,200-mile fence with barbed wire on top and surrounded by ditches and mines. Initial estimates for the cost of the wall had been around 100 million euros ($130 million), which would be raised through charities.

During its time as part of the Russian Empire and the Soviet Union, Ukraine's links to Russia negated the need for a real border, and most of its defensive attention over the past 100 years was focused on threats from NATO – particularly notable when you see that the majority of Ukrainian military bases are in the west of the country. Because of this, Ukraine's border with Russia remained notably weak. Writing for Businessweek in May, Denis Kazansky explained that far from looking like a well-fortified war zone, Ukraine's eastern border was a "poorly controlled strip of land that can be easily crossed."

"The state border runs right through the streets and courtyards of private houses," Kazanksy noted. "People there tell jokes about houses where the kitchen is in Ukraine and the toilet in Russia."

That loose border made it difficult for Ukraine to track any Russian citizens who may have made the journey across it. The borders were so faint that when Ukraine captured 10 Russian soldiers on their land, Russia just argued that these men had "crossed [the border] by accident on an unmarked section." Columns of tanks may have crossed the border with no resistance. While a barbed wire fence may ultimately prove no match for a traditional invasion, it could create difficulties for the type of stealth invasion Russia has been accused of.

In practical terms, building a wall along Ukraine's entire  border with Russia seems a dramatic step, and it's not yet clear whether Yatsenyuk actually plans to go that far.

Throughout history, however, governments have put up walls, from Hadrian's Wall and the Great Wall of China to Israel's barrier around the Gaza Strip and the border fence between the United States and Mexico. These obstacles are designed not only to keep people out, but also to deliberately delineate territorial borders – both issues in the current Ukraine crisis. Yatsenyuk himself knows the legacy. During an interview with the BBC in May, he accused Russian President Vladimir Putin of hoping to create a new "Berlin Wall."

Unfortunately, these walls don't always work.