# Central Bank Intervention > Central banks sometimes buy or sell their own currency to influence its value. Learn how intervention works, famous examples, warning signs and how traders respond. Source: https://learn.tradelabsai.com/forex/central-bank-intervention/ Track: Forex · Level: Intermediate · Updated: 2026-10-03 Publisher: TradeLabs AI (https://tradelabsai.com). Education, not financial advice. Cite as: TradeLabs Learn, "Central Bank Intervention", https://learn.tradelabsai.com/forex/central-bank-intervention/ Currency intervention happens when a central bank or finance ministry buys or sells currencies in the foreign exchange market to influence the exchange rate. A country whose currency has fallen too fast may sell foreign reserves to buy its own currency; one whose currency is too strong may sell its own currency to weaken it. Intervention can cause some of the sharpest moves in forex, and the threat of it shapes how traders position around key levels. ## Types of intervention | Type | How it works | |---|---| | Direct (spot) intervention | The authority buys or sells currency in the market | | Sterilised | The domestic money supply effect is offset with other operations, leaving interest rates unchanged | | Unsterilised | Money supply changes, which affects interest rates too | | Verbal intervention ("jawboning") | Officials warn they may act, hoping to move the market without spending reserves | | Coordinated | Several countries act together, which is usually more powerful | | Pegs and caps | A commitment to defend a level or range | ## Famous examples - **Plaza Accord (1985):** the US, Japan, West Germany, France and the UK agreed to weaken the dollar, which fell sharply over the next two years. - **Black Wednesday (1992):** the Bank of England raised rates and bought pounds to keep sterling in the European Exchange Rate Mechanism but failed; the UK left the mechanism, and speculators including George Soros profited. See [Famous Trades in History](https://learn.tradelabsai.com/history/famous-trades-in-history/). - **Swiss franc cap (2011 to 2015):** the Swiss National Bank capped the franc at 1.20 per euro, buying huge amounts of euros. On 15 January 2015 it abandoned the cap without warning, and the franc surged around 30% within minutes. - **Japan (2022 and 2024):** Japan's Ministry of Finance bought yen to slow its fall, including about ¥9.2 trillion in 2022 and further large purchases in 2024, according to official data. See [The ECB and the BOJ](https://learn.tradelabsai.com/macro/the-ecb-and-the-boj/). ## How intervention affects prices **Example: A yen intervention** USD/JPY has climbed rapidly to 160 as the gap between US and Japanese rates widens. Japanese officials repeatedly say they are watching moves with "a high sense of urgency". One afternoon, USD/JPY drops from 160.2 to 155.0 within an hour on heavy volume, with no economic news. Later data from the Ministry of Finance confirms large yen purchases. Traders who were long USD/JPY with tight stops are stopped out at poor prices; those positioned for the move profit. Weeks later, if the rate gap persists, USD/JPY may drift back up. ## Does intervention work? Evidence suggests: - **Short term effects can be large,** especially when intervention is a surprise or coordinated. - **Long term effects depend on fundamentals.** If interest rate differentials and economic conditions keep pushing the other way, intervention often only slows the trend. See [Interest Rate Differentials](https://learn.tradelabsai.com/forex/interest-rate-differentials/). - **Defending a weak currency is limited by reserves;** weakening a strong currency is limited only by willingness to create money, which is why the Swiss cap lasted over three years. ## Warning signs - **Rapid, one directional moves** that officials describe as "excessive" or "speculative". - **Escalating verbal warnings** from finance ministers and central bankers. - **Rate checks:** reports that a central bank has asked dealers for prices, often a final warning. - **Round number levels** that officials appear to care about. ## How traders manage intervention risk 1. **Reduce leverage** when trading against a currency that authorities are defending. See [Leverage and Margin in Forex](https://learn.tradelabsai.com/forex/leverage-and-margin-in-forex/). 2. **Expect gaps:** stops may fill far from their levels. See [Slippage](https://learn.tradelabsai.com/markets/slippage/). 3. **Avoid crowded positions** near levels that have triggered action before. 4. **Watch official statements and data releases** on intervention amounts. 5. **Remember the Swiss lesson:** a peg can end suddenly, and brokers may fail. Prefer well regulated brokers with negative balance protection. ## Frequently asked questions ### What is currency intervention? When a central bank or government buys or sells currencies in the market to influence its exchange rate. ### Why did the Swiss franc jump in 2015? The Swiss National Bank removed its cap of 1.20 francs per euro without warning, and the franc surged about 30% against the euro within minutes. ### Does central bank intervention work? It can cause large short term moves, but lasting effects usually require supportive fundamentals, such as changes in interest rates. Next, learn about the benchmark rates set each day in [FX Fixings: London and Tokyo](https://learn.tradelabsai.com/forex/fx-fixings-london-and-tokyo/). ## Continue learning - Next lesson: [FX Fixings: London and Tokyo](https://learn.tradelabsai.com/forex/fx-fixings-london-and-tokyo/) - Previous lesson: [Carry Trades in Forex](https://learn.tradelabsai.com/forex/carry-trades-in-forex/) - Related: [Carry Trades in Forex](https://learn.tradelabsai.com/forex/carry-trades-in-forex/): A forex carry trade buys a high yielding currency funded by a low yielding one. Learn how it earns, famous unwinds, funding currencies and how to manage crash risk. - Related: [Central Banks Explained](https://learn.tradelabsai.com/macro/central-banks-explained/): Central banks set interest rates and manage money to control inflation and support growth. Learn their mandates, policy tools, communication and market impact. - Related: [The ECB and the BOJ](https://learn.tradelabsai.com/macro/the-ecb-and-the-boj/): The ECB sets policy for the euro area and the Bank of Japan for Japan. Learn their mandates, tools like negative rates and yield curve control, and market effects. - Related: [Interest Rate Differentials](https://learn.tradelabsai.com/forex/interest-rate-differentials/): The gap between two countries' interest rates is a major driver of exchange rates. Learn why differentials move currencies, how to track them and their limits. - Related: [Leverage and Margin in Forex](https://learn.tradelabsai.com/forex/leverage-and-margin-in-forex/): Forex brokers offer high leverage through margin. Learn how margin is calculated, regulatory limits, margin calls and stop outs, and how to use leverage safely.