Russia left 'mainly kids' and conscripts to defend its borders, Ukrainian soldier says after surprise attack

• Ukrainian soldiers broke through the Russian border last week in a surprise attack.
• The operation's secrecy appeared to have caught Russian forces off guard.
• A Ukrainian soldier told The Wall Street Journal that Russian troops in the area were inexperienced.

Ukraine's invasion of Kursk was a surprise to many — and perhaps most of all to Russia.

Ukraine said it has gained control of nearly 400 square miles of Russia's Kursk region since last Tuesday, prompting the Kremlin to declare a state of emergency in the area.