Ukraine concluded its final day of missile tests near Crimea, despite Russia to shoot them out of the sky. The two-day S-300 surface-to-air missile exercises came and went without incident, but did nothing to calm fears of a possible full-scale war between the two nations.

The missiles were launched from Kherson, which borders the Crimea region Russia annexed in 2014. Ukrainian military officials say the exercises were successful, according to this report in the .

Russia responded by putting its air and ship defenses on high alert. Moscow claims the tests were too close to its territory and could endanger commercial planes traveling through its airspace. But the launches were conducted at least 18 miles away from Crimean airspace, Ukraine argued.

Missile tests of this kind are not unusual, but the unresolved conflict in eastern Ukraine, which is occupied by heavily equipped Russia-backed rebels that have claimed autonomy, has both sides on edge. The conflict began in December of 2013, when pro-EU protesters hit the streets after former President Viktor Yanukovych’s last-minute withdrawal from an EU association agreement; Yanukovych to Russia soon after.

It didn’t take long for pro-Russia rebels to revolt in the eastern regions of Donetsk and Luhansk and take over those territories with support from Moscow in 2014. For two years, Ukrainian and rebel forces have been waging war on and off. More than 9,100 people . Kiev is bracing for more bloodshed.

Ihor Dolhov, Ukraine’s Deputy Defense Minister, Russia has around 55,000 troops near its border and that at least 5,000 are operating inside of Ukraine, not including Crimea. Moscow’s for the build up is NATO’s growing presence in Eastern Europe, even though Ukraine is not a member of the alliance.

Ukrainian President Petro Poroshenko reporters recently that he could “not exclude a full-scale Russian invasion [of Ukraine] along all fronts.”

He is right to worry. Ukraine’s armed forces cannot fend off a full-on Russian offensive and Konstanin Kosachev, the Foreign Policy Committee chair in the Russian parliament, of that.

“Of course this would be the least desirable scenario, and all of us must work to prevent it... But eight years ago the leader of another country that was in conflict with Russia, I’m referring to Georgia, decided to test our military. And we all know how that ended. I hope Ukrainian officials remember the lesson from that experience.”

What makes the situation even more tense are in Kiev that Putin may feel emboldened to exacerbate the situation in Ukraine or elsewhere because of the presidential transition here in the U.S. President-Elect Donald Trump has vowed to warm relations with Putin in response to President Barack Obama’s tougher sanctions-based approach to Russia.

That Ukraine still pushed on with the missile tests proves it will not take the possibility of a Russian invasion lying down.

Jonah Blank, a senior political scientist at the RAND Corporation told Foxtrot Alpha that while Russia’s military is far superior to Ukraine’s, even the most powerful military cannot achieve air supremacy without taking out its adversary’s air defenses.

“Ukraine’s test of surface-to-air missiles is likely intended to signal that it would not submit to an air assault without a fight,” Blank said. “Russia would win such a battle—but perhaps at a cost it is unwilling to pay.”

Terrell Jermaine Starr is a freelance journalist in New York City who specializes in Russian-U.S. affairs and national security. You can follow him on Twitter .