As of Friday, the White House had officially selected three living veterans of the Afghanistan war to receive the Medal of Honor.

The number of living American troops who have been awarded the nation’s highest military decoration for service in Iraq: Zero.

It’s a curious twist in the history of America’s recent conflicts. While the Iraq war at its peak involved more troops than the Afghan war — and while far more American troops gave their lives in Iraq than have so far died in Afghanistan — neither President George W. Bush nor President Obama ever draped the medal around the neck of a service member being honored for gallantry in battle in Iraq.

Four U.S. servicemen did receive the medal for service in that conflict, but posthumously.

The absence of official recognition for a living soldier may raise some questions about the decision-making process in Washington. But there is at least one plausible explanation.

In Afghanistan, much of the fighting takes place in remote areas — and, in fact, all three of the living Medal of Honor recipients from the Afghan war have received the citation for action in mountainous regions along the border with Pakistan.

In some of those regions, the tough terrain makes it easier for the enemy to mass on U.S. forces, and the vast distances make it harder for attack helicopters to get into place. Intense firefights can stretch on for 45 minutes to an hour before helicopter support can arrive.

The result is that U.S. troops in Afghanistan have seen more situations in which small groups of personnel have found themselves caught in harrowing battles — without air support — and have been forced to make life-and-death decisions. In some of those battles, the troops who exhibited heroism have come out alive.

Such was the case with the three Afghan veterans selected so far to receive the Medal of Honor: Marine Cpl. Dakota Meyer, Army Staff Sgt. Salvatore Giunta and Army Sgt 1st Class Leroy Arthur Petry. (Overall, six U.S. servicemen from the Afghan war have been awarded the Medal of Honor.)

Of the four in Iraq to receive the medal posthumously, three died while throwing themselves onto live grenades to protect their comrades.

None of that is to detract from the heroism displayed by the troops in Iraq, or the terrifying conditions of battle there. But the conflict in Iraq was always more urban in nature. The kinds of firefights that have become common in Afghanistan just didn’t happen with the same frequency in Iraq.