If you're trying to understand the interjection/ejaculation soldiers exchange at any given point of their chatting, this is it. Never mind if it's lombard or else, though I believe its origin (in the song) is from Trentino (if you picked it from "Motorizzati a piè". I am half trentino and the linguistic analysis of the text here
http://www.unuciavezzano.it/canti_montagna.htm led me to that conclusion, further supported by this
http://www.corobrenta.it/armonie_di_un_popolo.html where you see at the bottom "provenienza Trentino"). In many Northern Italian dialects, including Lombard, Ligurian, Trentino, "l'è" means "it is"; in Piedmontese, we have the peculiarity of the verbal pronoun "a" ("i"/ "i-t"), a celtic loan, and we say "a l'é", shortened to "l'é".
By saying "l'è la naja" soldiers are really blaming on military life whatever goes bad/askew/wrong for them during their service. It's like saying in a different context "it's the recession", "it's 9/11", "it's the rogue governments". What soldiers believe is that once army life is over, they'll be OK! Yes, and talking about context, you know yours... so, guess right! Maurizio
The translation workplace 
