This was announced by the adviser to the Chief of Staff Ruslan Kavatsiuk at a briefing, Censor.NET reports citing Ukrainski Novyny.
He presented a preliminary analysis of the operational situation in the ATO area in August and September last year developed by the Main Operational Directorate of the General Staff and Central Research Institute of the Armed Forces.
"A more detailed report of the General Staff will be published before the end of the month," Kavatsiuk said.
According to a preliminary report, by early August last year, ATO forces were successful to encircle, block and destroy the enemy in the Donetsk and Luhansk regions.
On the night of 24 to 25 Aug., the territory of Ukraine was invaded by eight Russian battalion tactical groups of about four thousand soldiers.
The Donetsk and Luhansk regions were intruded by four enemy groups each.
This invasion turned the tide and led to encirclement of the ATO forces near Ilovaisk.
Russian military leadership failed to keep its promises to Ukrainian officers and gave the order to fire at the Ukrainian troops breaking out from the encirclement.
At the same time, a representative of the Central Research Institute of the Armed Forces Viktor Shydliukh said at a briefing the leadership of the Ukrainian army had been informed of the Russian invasion, but received verification of the data only on Aug. 25.
Shydliukh also noted the Ilovaisk tragedy was caused by an unauthorized retreat of individual ATO units from their positions and improper arrangement of strong points and checkpoints.