The Post’s Vernon Loeb has run 61 marathons, including 11 in Boston. Shortly after he finished the race Monday, he started reporting on the bombings. (The Fold/The Washington Post)

Vernon Loeb is The Washington Post’s Local editor. Monday’s Boston Marathon was his 61st marathon.

On my way to the lineup for the 117th Boston Marathon on Monday, I stopped and stood for a long moment on the finish line, a wide blue-and-yellow stripe painted across Boylston Street. It is hallowed ground for marathon obsessives like me who spend months every year doing fast, short runs during the week and slow, long ones on weekends so that we might one day be fast enough to qualify for this race.

I gazed at the empty bleachers on the south side of the street and the scaffolded structure over the finish line, beneath which thousands of elated and exhausted runners would pass later that afternoon. There’s no lingering here once the race is over, so a chance to stand quietly and savor the spot inspires enormous emotion.

Little did I know.

Had I glanced 10 or 15 yards down on the north side of Boylston Street, I would have seen the spot where the first of two bombs would explode during the race, killing three, injuring 176 and showing the world how impossible it is to secure the 26.2-mile course.

Vernon Loeb after running the 2013 Boston Marathon, minutes before Monday’s attack.

For someone bent on killing and maiming as many innocent people as possible, the Boston Marathon was a tailor-made target.

I crossed the finish line at 2:11 p.m., 39 minutes before the bombings. I’d been injured for much of the winter, hadn’t trained much and was hoping just to break four hours. I ran a 3:49 and was elated. I was about three blocks away, wearing my finisher’s medal and a metallic space blanket, when the bombs rocked what is always an exuberant post-race party.

I’m a former national security reporter. I wrote about the CIA for three years before Sept. 11, 2001, and began covering the Pentagon three months before the terrorist attacks. I soon found myself reporting on the wars in Afghanistan and, later, Iraq. A terrorist attack was hardly beyond my imagination. Right away, I knew that Monday’s explosions were bombs.

I remember once during a firefight in Fallujah how unprepared I was for the sheer volume of combat. What I heard reverberating down Boylston Street was way too loud to be some sort of industrial explosion — and the second blast only confirmed that.

Unable to take even a normal step, my knees aching and my calves knotting up, I typed a note on my iPhone to The Washington Post’s new executive editor, Marty Baron. He used to edit the Boston Globe, whose coverage of the Boston Marathon has always been spectacular.

Subject line: “Marathon bombs.” Message: “Seems like two bombs just went off near the marathon finish line, on Boylston St, in a instant, a hush fell over the post marathon scene, then the back bay erupted in sirens. CAnt call right now — no lines.”

Right before the bombings, I had realized that I was starving and started plotting where to find food as I made my way to my car, which I’d parked in the garage under the nearby Prudential Center. I’m a vegetarian, for the most part, but after running a marathon I crave fat and have been known to devour double cheeseburgers. I was planning to drive straight back home to Maryland and had loaded my cold packs in a cooler filled with ice so that I could strap them around my knees as I drove.

But then the bombs went off. My first thought was: I have to get to my car to get my notebooks.

So I trudged along, in some pain, and gathered up two legal pads and a handful of pens, leaving my laptop, my iPad and, most critically, my iPhone charger in my car. I can come back and get them after an initial round of reporting, I thought. But within minutes, Boston police had expanded the crime scene around the Prudential Center, stringing yellow tape between me and my Honda. I couldn’t get back to my car until Tuesday morning, hours after my iPhone ran out of juice.

I’m still struggling to comprehend someone bombing this race. I’ve run it 11 times, and it never gets old. I know the grueling, hilly course almost by heart. I’ve run it in 90-degree heat and in a nor’easter. I look forward to the challenge of qualifying year after year in a vain but glorious quest to stay one step ahead of age. The pageantry and the tradition of the race have a special hold on me, which is why it’s so hard to reconcile the joy of the event and the horror of the attack.

That is precisely the power of terror.

Patriots’ Day is a soulful holiday in Boston; the Red Sox play at Fenway at 11 a.m., and the rest of Red Sox nation lines the marathon course from its start in Hopkinton to Boylston Street, cheering with the brio only Bahston can muster.

For amateur runners the world over, pinning on a Boston bib is like playing in the World Series or the World Cup. We never see the Kenyans and Ethiopians who win in times that hardly seem possible. But running in the same race with them is still a thrill, given the marathon’s history and the lore of the rolling terrain that burns up runners’ quadriceps and then offers the ultimate test, late in the race, called Heartbreak Hill. If you have something left at the top of Heartbreak, a great race might be yours. The final five miles are fast and mostly downhill. The adrenaline that comes with the turn onto Boylston Street, with the finish line 600 yards ahead, is addictive.

This year, the biggest heartbreak was not in Newton at the 21-mile mark. It was a few yards from the finish line.

Marathon running is not for everybody, but it isn’t as hard as it seems. Most people can run one if they train properly, and finding out what your body is capable of is amazing. For some, it’s life-altering. I’ve seen people go from couch potatoes to marathoners in nine months, transforming their self-image.

Hundreds of thousands of people wouldn’t be running marathons if they weren’t getting something out of it physically and, even more important, mentally. I run to quiet the mind, to escape e-mail, texts, phone calls and Facebook, to find the off switch.

Even under the best of circumstances, though, marathon running can be hazardous to your health. Some people break down and can’t handle the mileage required by the normal 18-week training cycle. On race day, you can suffer heatstroke from dehydration or hyponatremia from drinking too much water. Or you can have a heart attack on the course — that’s happened to men in numerous marathons I’ve run.

After last year’s 90-degree scorcher in Boston, about 150 people remained in the hospital the day after the race. But a comforting aspect of the Boston Marathon has always been the medical talent the city commits to runner safety. World-class emergency room physicians populate the medical tent just past the finish line, and solicitous nurses and medical personnel ask if you’re okay at the even slightest wobble.

This year, the medical personnel deployed like combat doctors, racing down Boylston Street, where they stabilized 90 victims and loaded them into ambulances in half an hour. Without their presence at the finish line, more people undoubtedly would have died.

I ran my first Boston Marathon in 1996, the 100th running, when race organizers opened up the field and let more than 38,000 runners participate. When my oldest daughter was a student at Boston University, I ran four in a row from 2007 to 2010. She and her friends would make signs and cheer me on. We’d have a big party after the race, and the tradition was that I would give my finisher’s medal to whomever came up with the best cheer.

I warmly remembered those days on Monday, before the bombs went off and Boylston Street was covered in blood.

I would never equate the importance of running marathons with the persistence and dedication we ask of our counterterrorism professionals. But both fields demand intense preparation and a belief that little successes now can mean finishing a race months later. There is no instant gratification in either. Victory is elusive in both. Most marathon runners never win a race, they only finish. Counterterrorism officials, similarly, are fighting a war they never win. But like marathon runners, they carry on. Whether they’ve succeeded or failed comes down to how smart they’ve been and how hard they’ve tried.

People who hunt terrorists never sleep well at night, in my observation. I remember then-CIA Director George J. Tenet, in the years before Sept. 11, taking his classified briefing on the dangers of al-Qaeda around Washington, pleading for attention. I remember thinking that Richard Clarke at the National Security Council was obsessed with Osama bin Laden, for good reason. I’ll never forget how John P. O’Neill, the FBI agent who spent his career hunting down Islamic terrorists, got pushed out of the bureau, went to work as security director for the World Trade Center in New York — and died in the 9/11 attacks.

They would have been great marathoners.

In the days after Sept. 11, I often wondered why al-Qaeda, in its quest to sow terror and attack the United States, didn’t stage smaller bombings at cafes and shopping malls. I figured it hadn’t happened because the United States had made such attacks significantly harder to pull off after 9/11.

We’ve now seen that bombing an open, crowded event such as the Boston Marathon is something determined terrorists can manage. The course is long. The crowd is dense. The bombing underscored an attacker’s asymmetric advantage: While authorities have to defend 1,000 targets, a terrorist need only hit one.

The bombs on Boylston Street made running a marathon seem trivial. But what each of us gets out of this particular obsession feels more essential now, not less. If nothing else, running helps power us through the insanity. We’re a determined bunch, a little nuts, perhaps, and my sense that is most of us will respond by saying that we’re not going to let terrorists take our sport away.

President Obama said as much at an interfaith prayer service for the bomb victims on Thursday. “We will all be with you as you learn to stand and walk and, yes, run again. Of that I have no doubt,” he said. “You will run again.”

I, for one, am signing up to run the Delaware Marathon in Wilmington on May 12. I should be able to take my Boston time down to qualify for next year’s race.

I bet it will sell out in record time.

Read more from Outlook:

Five myths about marathons

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