By Andrew Osborn

(Reuters) - A new school textbook that likens Russia's war in Ukraine to the Soviet struggle against the Nazis and says Russia was "forced" to send troops into Ukraine was presented in Moscow on Monday.

President Vladimir Putin casts the war, which Moscow officially calls a "Special Military Operation", as a difficult but necessary fight against a Western- and NATO-backed Ukraine. He says it is part of a wider existential battle against a decadent West trying to weaken and dismember Russia.

For their part, Ukraine and its Western allies say Russia is waging a brutal and unprovoked war, merely to gain territory.

The three-volume "Military History of Russia" was edited by Vladimir Medinsky, an aide to Putin who headed a delegation that held unsuccessful peace talks with Ukraine in 2022, in the early months of the war, and has already co-authored Russia's main history textbook.

The third volume, likely to be dismissed by Ukraine's leadership as propaganda, is designed to be taught to children aged 15 and older.

It explains why the Kremlin believes the war started and how it is being fought, highlights what it regards as incidences of battlefield heroism, and describes how the modern Russian army is sometimes employing techniques used by the Soviet army during World War Two.

In a chapter entitled "Professionalism, indomitability and courage: Russian troops in the Special Military Operation", the book tells schoolchildren that Russia was "forced" to send its troops into Ukraine in 2022.

It says the West had for years ignored Russia's security concerns - a reference to the eastward expansion of the NATO military alliance, and to what the book described as the Western-backed toppling of a Russia-friendly Ukrainian president in 2014, which had turned Ukraine into an "aggressive anti-Russian bridgehead".

NATO and Ukraine deny ever posing a threat to Russia.

Speaking at a TASS news conference to discuss the new book, Ivan Basik, a military historian affiliated with the Russian army, said Western and Ukrainian actions had made the war "inevitable".

"The most important task was to explain to the younger generation, to schoolchildren, the forced nature of the special military operation carried out by the Russian Federation," he said.

(Reporting by Reuters; Writing by Andrew Osborn; Editing by)