Recently, I've noticed the dollar index hovering around 98.40, which indeed reflects the market's sensitive response to geopolitical changes. During the spring of last year, when US-Iran diplomatic tensions escalated, the dollar index experienced a noticeable decline, as market sentiment shifted quite quickly at that time.

Speaking of which, as a key benchmark measuring the strength of the US dollar globally, the logic behind its fluctuations is actually quite complex. This index mainly reflects the performance of the dollar against six major currencies, including the euro, yen, and pound, with the euro carrying the largest weight. At that time, the European Central Bank's policy stance was also adjusting, which supported the euro and consequently exerted downward pressure on the dollar index.

From a technical perspective, the 98.40 level is indeed a critical point. If this support zone is broken, the dollar could face a deeper correction. Data from the Commodity Futures Trading Commission also shows that traders' net long positions in the dollar are decreasing, reflecting a shift in market sentiment.

But what’s truly interesting is the linkage between geopolitics and commodities. US-Iran relations directly influence oil supply expectations, as Iran holds the world's largest proven crude oil reserves. When diplomatic negotiations signal positive developments, the market anticipates increased Iranian oil exports, putting downward pressure on oil prices. Since oil is priced in dollars, falling oil prices often weaken international demand for the dollar, further pushing down the dollar index. Meanwhile, gold prices tend to move inversely to the dollar index; when the dollar weakens, dollar-denominated gold tends to rise.

Another important backdrop is the US domestic economic data. Last year, inflation data showed signs of easing, leading markets to expect that the Federal Reserve might not be as aggressive in raising interest rates. Core PCE inflation's monthly increase slowed to 0.2%, and non-farm employment growth also cooled down gradually. As expectations for US rate hikes diminished, the yield advantage of the dollar weakened, making other currencies more attractive.

Options market volatility premiums increased noticeably at that time, indicating traders anticipated greater price swings in currency pairs. Under such circumstances, traditional risk appetite rotations would activate, with capital flowing from safe-haven assets into risk assets.

Interestingly, similar situations have occurred in history. During the initial phase of the Iran nuclear deal negotiations in 2014-2015, the dollar index also experienced significant weakness. However, the context then was quite different from last spring; at that time, the Fed was preparing for its first rate hike, global inflation remained subdued, and oil prices plummeted from over $100 to around $50. The current environment is entirely different—global inflation has eased from multi-decade highs, oil prices are oscillating within a relatively high range, and the baseline levels are elevated.

For investors, the movement of the dollar index reflects how the market gradually prices in geopolitical possibilities. It’s not just a reaction to a single event but a progressive process. When risk sentiment improves, the appeal of the dollar as a safe-haven asset diminishes, and capital seeks higher-yielding investment opportunities. Yet, the dollar’s long-term position is still supported by deep structural factors, such as the liquidity of the US Treasury market and the dollar’s role as the world’s primary reserve currency.

Therefore, the performance of the dollar index during that period serves as a good barometer, reflecting a combination of technical price trends, geopolitical risk assessments, and monetary policy expectations. For those paying attention to global capital flows and market volatility, the dollar index’s movements are always worth close monitoring.