According to US estimates, Russia has sent more than 100,000 troops near the Ukrainian border in recent weeks, raising concerns from Western and Ukrainian intelligence officials that an invasion could be on the cards.
The West said Russia has created pressure points on three sides of Ukraine - Crimea in the south, Belarus in the north and on the Russia - Ukraine border.
According to CNN, these are three fronts that Ukraine and the West are monitoring, and recent moves by Russia have been spotted on each front.
Eastern Ukraine
Most of the attention has been on the breakaway areas of Donetsk and Lugansk, where Ukrainian forces and the breakaway have been in conflict since 2014.
The most important necessity for those who follow Russia's moves is that Moscow can increase the military power it already has in the region, thereby making eastern Ukraine the easiest location for an invasion.
Satellite images collected by CNN show a large base in Yelnya, which houses Russian tanks, artillery and other armored vehicles, which has been largely cleared. The devices appear to have moved much closer to the border in recent days.
A large number of weapons were transferred to the base by the end of 2021 before disappearing - including about 700 tanks, infantry fighting vehicles and ballistic missile launchers. Social media footage since then shows some of the devices on trains and roads much further south in the Bryansk region, near Ukraine.
Stephen Wood, senior director of satellite imaging company Maxar, told CNN: "To me, it seems a significant number of vehicles (tankers, self-propelled artillery and other support vehicles) have departed from the northeastern parking lot; additional armored vehicles have departed from the more central parking lot."
Meanwhile, increased activity in Kursk and Belgorod, which border northeastern Ukraine, has added to concerns.
Konrad Muzyka, a military movements monitoring expert at Rochan Consulting, warned on Twitter: "We are seeing a large number of vehicles and personnel in Kursk."
Phillip Karber of the Potomac organization in Washington, who has also studied the Russian military's movements in detail, told CNN this month: "Russia's most powerful attack formation - theFirst Guards tank Army, which is based in the Moscow region - has moved 400 km south and is focusing in the optimal area for a rapid armored attack on the Khursk-Kiev route."
Belarus
The West is also concerned that a large number of Russian troops in Belarus - a close ally country that could provide another path to enter Ukraine.
Russia and Belarus began a 10-day joint exercise on February 10, the scale and duration of the exercise have raised concerns in the West.
Russia's deployment of Belarus is said to be the largest since the Cold War, with "an estimated 30,000 fighters, Spetsnaz special forces, fighter jets including Su-35, Iskander double missile and S-400 air defense system," NATO Secretary General Jens Stoltenberg said on February 3.
This is also the largest exercise that the Belarus armed forces will conduct at any time of the year, according to the Center for Strategic and International Studies (CSIS). The Russian Defense Ministry said the purpose of the exercise, called "Allied Resolve-2022", included repelling "outside aggression".
Earlier this month, a European diplomat told CNN that the concentration of Russian forces in Belarus would be the missing piece Moscow would need to launch a quick attack on the Ukrainian capital.
Meanwhile, CSIS warned that joint drills will also create cover for a Riverside move through Belarus and into northern Ukraine.
And satellite images released by Maxar appear to show that the Russian military has deployed advanced troops at several locations in Belarus. The deployment activities may involve joint drills, but other photos show the camps set up near the border with Ukraine, hundreds of kilometers away from the drill site.
However, if Russia focuses on the Belarus border as a point of entry into Ukraine, this route will face many difficulties. Russian soldiers will have to cross the Pinsk sludge, also known as the Pripet Marshes, one of the largest flooded areas in Europe, located between the border between Belarus and Ukraine - a forested, flooded terrain with many forests stretching over 270,000 square kilometers. The area has hindered the German Fatherland Front's forces in the Barbarossa Campaign, Germany's invasion of the Soviet Union, in 1941.
Crimea
The peninsula, which was annexed by Russia in 2014, will provide a natural foundation for any new operation, but it is unclear whether Moscow intends to make a move into Ukraine from Crimea.
Satellite company Maxar has observed a large deployment of troops and equipment, assessing that more than 550 tents and hundreds of vehicles have reached the north of the capital Simferopol of Crimea.
A new deployment was then identified by Maxar for the first time on 10 February near the town of Slavne on the northwest coast of Crimea, including armored vehicles.
The new deployment was observed on the same day as a number of Russian warships arrived at Sevastopol, the main port of Crimea. The Russian Defense Ministry posted images of six bulky landing ships at the port on February 10.
The Ukrainian Navy responded that "Russia continues to Militarize the Black Sea region, transferring more landing ships to put pressure on Ukraine and the world. The Ukrainian Navy is ready for any scenarios and provocations to protect the country."
Meanwhile, Russian officials have repeatedly denied Western accusations of a plan to invade Ukraine. Russia insists the deployment was carried out within its territory and was not intended to attack any side.
