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.

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.

The deputy commander of a squad involved in the offensive told The Wall Street Journal that they had anticipated more resistance from Russian troops.

"They were mainly kids doing their mandatory service," said the unnamed commander, who goes by the call sign Pokemon.

He said they took three prisoners; the youngest was 19.

"Everybody is more or less happy with how it's going," he told the outlet.

Russian men aged between 18 and 30 are required to undertake one year of military service. The maximum age was raised last year from 27.

The commander added that he only found out about the Kursk offensive shortly before it kicked off.

The Ukrainian military seemed to go to great lengths to keep the mission a secret. The New York Times reported that a research institute affiliated with the military had analyzed invasions in modern history and found that the most successful operations were kept private before being carried out.

A Ukrainian deputy brigade commander told The Times that most senior officers were only given three days' notice before the invasion took place. Meanwhile, soldiers in non-senior roles were only given one day's notice, the report added.

The influential pro-Kremlin account Rybar wrote last week that Russia's military top brass had been monitoring a Ukrainian buildup for the past two months but did little to prepare.

"It appears that yet again, in the past few days, the Ukrainians have surprised Russia, and observers in the West, with their latest operation," Mick Ryan, a war analyst and retired Australian major general, wrote in a recent analysis.

This is in contrast to Ukraine's failed counteroffensive last year. After pushing back against Russian defenses in the south, troops were only able to regain around 200 square miles of territory.

Before the attack, Ukraine's military released a teaser video and telegraphed about its intention months in advance.

This time around, most onlookers "didn't think they had the forces up their sleeves spare to do this," Patrick Bury, a military analyst at the UK's University of Bath, previously told Business Insider.

It's worth noting that the extent of Russia's knowledge of a potential attack is not known. Writing in a Telegram post on Friday, Russian military expert Vladislav Shurygin said Russian commanders had ignored intelligence that Ukraine was preparing to attack and failed to initiate defense protocols.

Sergei Markov, a Kremlin-connected political analyst, told The Washington Post that "the signal came from intelligence to the leadership, but … measures were not taken."

"This is a failure of the entire system of intelligence, and since Putin is responsible for this, then it's clear this is a blow to Putin," he added.

Rainer Saks, an Estonian security expert, told ERR that the Ukrainian invasion of Kursk had been successful "mainly due to the fact that the Russian military command and political leadership were completely unprepared for this kind of event."

Representatives for Ukraine's Armed Forces and Russia's Ministry of Foreign Affairs did not immediately respond to requests for comment.