A lonely impulse of delight Drove to this tumult in the clouds; (11-12)
The speaker didn't join the air force on account of some patriotic feeling. He was driven by his own unique, internal impulse.
The years to come seemed waste of breath, A waste of breath the years behindIn balance with this life, this death (14-16)
The ultimate patriotic statement is here: dying for one's country in war makes the rest of one's life seem like a waste of breath. Hmm, this is strange, given the weird absence of patriotism from many of the speaker's other remarks. Perhaps this is ironic, or perhaps the speaker has just changed his mind.