In the book A Seperate Peace, why is it ironic that the carnival ends with the arrival of Leper's telegram announcing his escape?

The Winter Carnival creates the "special illusory and
separate peace" that lends the novel its title.  The boys create an escape through
sports that removes them not only from the reality of the war, but from there lives at
Devon as well.  The games, along with a little spiked cider create a feeling of
happieness and comradery that, although fleeting, highlights the innocence of the boys. 
Leper's telegram interrupts this celebratory feeling, literally penetrating the
sheltering walls of the school as the war will soon.  The telegram is ironic because
Leper should have been among the boys at the carnival; instead he is traumatized by his
brief experience with the army.  The telegram is cryptic but Gene understands that Leper
is home in Vermont.  Gene travels to Vermont by train in the next chapter - notice the
language Knowles uses to describe this journey into the cold
night.