As Russia advances on several cities in Ukraine, a closer look at each country's military muscle suggests Russia may have a distinct advantage.

According to Global Firepower, which analyzes data from 140 military powers around the world, Russia outranks Ukraine in nearly every metric. Ukraine's annual spending on its military is less than one-tenth of what the Kremlin spends, which is reflected in the forces and war chest of each country.

Russia currently has 850,000 active personnel in its military, while Ukraine has 200,000. In the lead up to the invasion, Russia encircled Ukraine with more than 150,000 troops.

In terms of weapons and transport, Russia also outguns Ukraine. When fighting on land, Russia has five times as many tanks and more than two times as many armoured vehicles in its arsenal as Ukraine. By air, Russia has more than 10 times the number of fighter aircraft and around 16 times the number of attack helicopters of its neighbour.

Ukraine is getting military support in the form of aid and supplies from countries such as the U.S., Turkey, Estonia and Canada, which has sent lethal aid to Ukraine worth nearly $10 million. Ukraine's military also has experience defending against the Russians, particularly in the Dombass region where they have been fighting separatists backed by Russia since 2014.