MOSCOW — There's a book being published exclusively in the United States entitled, Brothers Armed: Military Aspects of the Crisis in Ukraine, written by Russian experts of the well-known, Moscow-based Centre for Analysis of Strategies and Technologies. The word "brothers" may sound like it's taken from Communist propaganda, but the word is actually apt.

After the collapse of the USSR in 1991, both the Russian Federation and Ukraine inherited what was left after the Red Army. The Ukrainian share was significant. Moreover, the Ukrainian army at that time was equipped better than an average Russian battalion.

The units located on Ukrainian territory were known as the "second-line army," because it was their job to stop the enemy if it got past the first line of defense. They were stretched along the Western borders of the Warsaw Pact. Because of its strategic importance, Ukrainian units had to have the best equipment at their disposal.

As for the nuclear weapons, they were returned to Russia in exchange for the territorial integrity of Ukraine, guaranteed by Moscow, Washington, London, Paris and Beijing. Last year, the world witnessed those promises being shattered.

In the post-Soviet era, both armies have shared the same destiny — namely, a slow degradation.

The Russian forces, which numbered 5 million people, accumulated a great number of weapons and equipment for the additional millions of conscripts who would be drafted in case of war. This tradition of maintaining a huge military arsenal fueled by universal conscription survived the Soviet empire.

But it failed to be effective in both Chechnya wars. Over time, Russian divisions — apart from the landing troops and special forces — turned into tank storages.

Post-Soviet armament

Of the two "brothers," Ukraine first turned the page on post-Soviet traditions. Under the rules of President Leonid Kuchma (1994-2005), Ukraine made its first steps towards joining NATO. The dreams of joining the organization rushed army modernization. The focus was shifted to small units ready to fight at any time, which gained experience in Iraq and Afghanistan.

The situation changed completely after the war between Russia and Georgia in 2008. Although Russia won, the war exposed the weaknesses of the Russian army and pushed Moscow towards a thorough reorganization of its forces.

According to the Brothers in Armsauthors, Russia plans to spend some $353 billion on military buildup between 2010 and 2020. The end of the Georgian war saw military salaries rise by between 250% and 300%.

The Caucasian war had just the opposite effect on Ukraine. Its hopes for joining NATO were dashed, and with it the enthusiasm for army modernization. Lack of funding resulted in a further military decline. The confrontation in Crimea, in March of last year, fully revealed how advanced the process was.

As the situation on its eastern border worsens, Ukraine is being forced to catch up on army modernization during an actual war. Soldiers are trained under the fire of separatist troops, and new weapons are being immediately tried on the battlefield.

Even though these don't seem like the optimal conditions for forging a new army, Brothers in Arms co-author Vyacheslav Tseluiko says Ukrainian forces are gaining experience and strength, and becoming increasingly dangerous for a potential enemy.

In addition, Ukrainian commanders seem to have found an effective defense strategy. All the forces are concentrated in big cities, turning them into fortresses. An attempt to siege those causes major loss of life. The separatists' unsuccessful attempt to occupy Mariupol proved this tactic to be effective.

Russian commanders understand that an open war with Ukraine would be difficult and bloody. To occupy Kiev and Warsaw within two weeks — as Putin once declared possible — would not in fact be achievable. Which is probably why Russia has so far withheld a frontal attack.