https://www.bbc.com/news/live/c8dpgeq01n0tUkraine’s advance into Russia has slowed in recent days and there’s likely to be a point soon when it stops.
There’ll be more logistical challenges the further Ukraine advances – keeping forces supplied with ammunition, food and fuel.
But that’s not a significant obstacle given that Ukraine’s troops are still within 50km of their own border.
The greater concern will be holding on to the gains made – long enough for it to be a bigger political problem for President Putin and a drain on Russia’s own forces.
There’s already evidence that Ukraine has been digging in and building defences. But those defences will become a magnet for Russian attacks.
Moscow has already been releasing video of its air force using glide bombs to target Ukrainian positions on its side of the border. The same weapons which have had such a devastating effect in eastern Ukraine.
Justin Crump, a former British Army Officer and who now heads the risk consultancy Sibylline, says over time Ukrainian forces across the border will become more vulnerable to Russian attacks. He says the chances of Russia attacking Ukraine’s supply lines and using its Air Force effectively will increase.
The morale boost for Ukraine in launching this offensive could soon dissipate if this becomes another grinding, static battle.