When it comes to disclosing the true cost of the war in Ukraine for Russia, the Kremlin has rarely, if ever, chosen to be honest. But occasionally, things slip out.

Last Wednesday, Mikhail Teplinsky, commander-in-chief of the Russian Airborne Forces, congratulated his troops on the anniversary of the division’s founding. He said how proud he was of the ‘special military operation’ in Ukraine and reeled off the number of soldiers honoured as ‘Heroes of Russia’, as well as the 30,000 who had received other honours from the state. A video of his speech, below, was posted to the Russian ministry of defence’s social media channels and website.

But the video was taken down quickly because Teplinsky let some other figures slip. ‘I am most proud of the fact,’ he said, ‘that more than 5,000 injured paratroopers returned to the front after treatment, and more than 3,500 of our injured refused to leave the frontline at all.’ In other words, Teplinsky had admitted that, since February last year, more than 8,500 paratroopers had been injured fighting in Ukraine. Both sides try to avoid mentioning casualty figures – they’ll be steep on both sides.

Teplinsky’s mistake was widely circulated on Russian social media and picked up by intelligence agencies, including Britain’s. He didn’t say how many troops the air force had lost since the invasion began, or how many paratroopers were too badly injured to return to battle. But his disclosure is significant as it informs assessments into just how many fatalities there have been. Britain has been doing the sums and extrapolations.

The last time the Russian government made any statements regarding losses in Ukraine was in September. At the time, Russian defence minister Sergei Shoigu stated that 5,937 Russian soldiers had been killed in just over six months of war – a figure regarded as a gross underestimate at the time. But classified Russian intelligence documents picked up by the Pentagon, which were revealed in April following a leak, revealed that the FSB believed the number of Russian casualties to be closer to 110,000.

In 2015, Moscow announced plans to grow its air force to 60,000 troops. Assuming this was roughly the figure as of last year’s invasion, Teplinsky’s disclosure that at least 8,500 were wounded means that at least 14 per cent of the air force’s total number has been injured in some capacity since then. Given that only half of them will have been deployed, it suggests that an even higher proportion have probably been hit since the invasion began.

Picking up on Teplinsky’s disclosure, the British Ministry of Defence has said the figures fit its assessment that at least half of the 30,000 paratroopers believed to have been deployed to Ukraine last year have been killed or injured. With no sign that the war is any closer to ending, this number will continue to rise. An autocracy’s tolerance of casualties may be pretty high, but the same was said of the Soviet Union. The 15,000 Russian lives lost in during the Afghan campaign in the 1980s were seen as a major factor in the collapse of the regime. This figure pales in comparison to the number of presumed deaths in Ukraine.

It is unlikely that we shall know the true cost for Russia of Vladimir Putin’s invasion until the war ends. But as Teplinsky’s video shows, the Kremlin won’t be able to keep the number of Russian lives lost a secret forever.