Lyric discussion by sweatersdotcom 

Cover art for Chicago lyrics by Portugal. The Man

i think this song is just a statement on the war, or war in general. the line "send me to the battle please sir!" is a pretty obvious tip in that direction, but there are a few other such references.

"the pig's spitting taxes and unwanted tasks" i'm sure most of you are aware how frequently pigs are used as symbols for officials, especially corrupt ones. see Animal Farm, or the song Pigs by Pink Floyd, or the song War Pigs by Black Sabbath. and he's spitting taxes, which the people have to pay to finance the war.

the image of a city burning, not necessarily Chicago, is a pretty powerful piece of imagery associated with war.

"send your money for the caterpillars to entertain" this line sounds like nonsense at first, but.. the treads of tanks are commonly referred to as caterpillar treads. it could be a metaphor for "support the troops" donations and increased taxation going to finance tanks which then go out and "burn the motherfuckers down"

of course I could be completely wrong. but anybody care to add to this?