Russian soldiers refused to complete their duty and expressed 'moral exhaustion,' and 'worsening' of health in 10 letters left behind in Izium, Ukraine, The Washington Post reported

• Ukrainian forces recaptured the city of Izium on September 9 after months of Russian occupation.
• In their hasty retreat, Russian soldiers left behind letters and other belongings, per WaPo report.

About 10 days before the Ukrainian military recaptured the city of Izium in the Kharkiv region on September 9, Russian soldiers wrote at least 10 letters to their superiors, asking to be relieved from active duty due to "moral exhaustion," "worsening" health, and a lack of vacation time to see their families.

"I refuse to complete my duty in the special operation on the territory of Ukraine due to lack of vacation days and moral exhaustion," one person identifying himself as a commander wrote, per a letter obtained by The Washington Post.

The 10 letters, dated August 30, were among many belongings left behind in Izium as Russia's military made a hasty retreat from the region after months of occupation.

Ukrainian soldiers provided original copies of the letters to The Post, which reported on the correspondence. Some of them were also posted on Twitter. The Post, however, made it clear the authenticity of the letters has not been confirmed by independent forensic experts.

One soldier wrote that he hoped to be released from his duties because of "the worsening of my health and not receiving the necessary medical aid." Another wrote he was experiencing "physical and moral exhaustion," The Post reported.

Other letters revealed that Russian soldiers were not receiving vacation time and missed significant family events such as marriages or seeing the birth of a child.

The 10 letters appeared to be written in a similar fashion, The Post reported, suggesting that they were written together.

The contents of the letters also share some of the weary sentiments other Russian soldiers have expressed in recent days as Ukrainian forces reclaim thousands of square miles of land.

In a call that was intercepted by Ukrainian intelligence, a Russian soldier told his father, "Everything's bad, pop ... We're losing, definitely, on top of that."

The extent of the casualties in the Kharkiv region is slowly coming into a clearer view.

On Thursday, a mass grave site with at least 440 bodies was found in Izium, according to a tweet from Iuliia Mendel, the former spokesperson to Ukrainian president Volodymyr Zelenskyy, and other reporters.