IN RECENT weeks the world economy has been on a war footing, at least  rhetorically. Ever since Brazil’s finance minister, Guido Mantega,  declared on September 27th that an “international currency war” had  broken out, the global economic debate has been recast in battlefield  terms, not just by excitable headline-writers, but by officials  themselves. Gone is the fuzzy rhetoric about co-operation to boost  global growth. A more combative tone has taken hold (see 
article).  Countries blame each other for distorting global demand, with weapons  that range from quantitative easing (printing money to buy bonds) to  currency intervention and capital controls.
 Behind all the smoke and fury, there are in fact three battles. The  biggest one is over China’s unwillingness to allow the yuan to rise more  quickly. American and European officials have sounded tougher about the  “damaging dynamic” caused by China’s undervalued currency. Last month  the House of Representatives passed a law allowing firms to seek tariff  protection against countries with undervalued currencies, with a huge  bipartisan majority. China’s “unfair” trade practices have become a hot  topic in the mid-term elections. 
  A second flashpoint is the rich world’s monetary policy,  particularly the prospect that central banks may soon restart printing  money to buy government bonds. The dollar has fallen as financial  markets expect the Federal Reserve to act fastest and most boldly. The  euro has soared as officials at the European Central Bank show least  enthusiasm for such a shift. In China’s eyes (and, sotto voce,  those of many other emerging-market governments), quantitative easing  creates a gross distortion in the world economy as investors rush  elsewhere, especially into emerging economies, in search of higher  yields.
A third area of contention comes from how the developing countries  respond to these capital flows. Rather than let their exchange rates  soar, many governments have intervened to buy foreign currency, or  imposed taxes on foreign capital inflows. Brazil recently doubled a tax  on foreign purchases of its domestic debt. This week Thailand announced a  new 15% withholding tax for foreign investors in its bonds.