One retiree, Yuriy Medynsky, 84, said he had drawn on his meager benefits to send a message not once but repeatedly to honor his grandson, who was 33 when he was killed fighting in the Kharkiv region in the spring of 2022.

“To Katsap hermits for Maksym Medynsky. Grandpa,” he wrote, using an epithet for the Russians.

“I put in my message all the hate I feel for Muscovites,” Mr. Medynsky said. He paid about $13 for each message.

His daughter-in-law, Tetyana Medynska, Maksym’s widow, has also sent repeated messages.

“Personally for me it’s a tiny bit of revenge,” she said. “I do not imagine killing someone particular, as they are all guilty, all Russians who came to Ukraine. They have no faces for me. When I send money for the message on the bombs, I feel some kind of psychological relief.”

Some have struck a tone of irony.

“When my friend got married, she asked to write her maiden name on the mortar, to say farewell to it,” said Private Vladyslav, a soldier at a mortar position outside the town of Toretsk, in eastern Ukraine.

He himself once sent a message: “I congratulated my mom on her birthday this way,” Private Vladyslav said.