Better examples:
Soviet Union in WWII. With a combination of Ideology, patriotism, and an absolutely murderous opponent, the USSR sacrificed more than 27,000,000 of their own people, or at least 5 times the casualties they inflicted, but kept fighting until they and their allies crushed the enemy.
France in WWI: lost almost half of all the men in the country between the ages of 20 and 40, but the enemy ended up crying for an armistice first, despite a lower percentage of loss.
Some combination of 'patriotism' brought on by the nature of the enemy, your own culture and history, and the adroitness of your own government/leaders in invoking them should modify War Weariness. Note that Stalin very carefully did not tell his people to fight for Communism: the most common wartime popular slogans, invoked on the sides of tank turrets, in official orders and posters, were za Rodinu! - 'For the Motherland', and 'Death to the Fascist Occupiers!' - the first completely traditionally patriotic, the second invoking the murderous policies of the Nazis.