One of three active-duty Marines who stormed the U.S. Capitol together was sentenced on Monday to probation and 279 hours of community service — one hour for every Marine who was killed or wounded fighting in the Civil War.

U.S. District Judge Ana Reyes said she can’t fathom why Dodge Hellonen violated his oath to protect the Constitution “against all enemies, foreign and domestic” — and risked his career — by joining the Jan. 6, 2021, riot that disrupted Congress from certifying President Joe Biden’s 2020 electoral victory.

“I really urge you to think about why it happened so you can address it and ensure it never happens again,” Reyes said.

Dodge Hellonen, now 24, was the first of the three Marines to be punished for participating in the Capitol siege. Reyes also is scheduled to sentence co-defendants Micah Coomer on Tuesday and Joshua Abate on Wednesday.

The three Marines — friends from the same unit — drove together from a military post in Virginia to Washington, D.C., on Jan. 6, when then-President Donald Trump spoke at his “Stop the Steal” rally near the White House. They joined the crowd that stormed the Capitol after Trump urged his supporters to “fight like hell.”

Before imposing Hellonen’s sentence, Reyes described how Marines fought and died in some of the fiercest battles in American history. She recited the number of casualties from some of the bloodiest wars.

After walking to the Rotunda, they placed a red “Make America Great Again” hat on a statute and took photos of it. They remained inside the Capitol for nearly an hour, joining other rioters in chanting “Stop the Steal!” and “Four More Years!”

None of them are accused of engaging in any violence or destruction on Jan. 6. But prosecutors said none of them have expressed sincere remorse for their crimes.