But the first country to send a missile, even a non-nuclear one, could trigger a tit-for-tat set of reprisals that both sides could find hard to stop.

ECONOMIST: South Asia’s nuclear winter | The

If trade policies are deemed to hurt a tradig partner, a trade war can erupt, in which countries ratchet up protectionist policies in a tit-for-tat manner, ultimately leading to economic slowdown.

FORBES: Eight Biggest Global Trade Offenders

"Clearly some supporters feel aggrieved that a song they believe to be no more than a tit-for-tat 'wind up' of Celtic supporters should be singled out in this way and merit the attention of police, governments and anti-racism organisations, " said Bain.

BBC: Bain responds to 'Famine song'