Obama escorted a group of nine children from military families onto the field before the game, where they each took a spot on the diamond after delivering the first pitch.
Second baseman Danny Espinosa caught the pitch, then trotted to the mound, where Obama offered him a hug and Espinosa took pictures with the group. Espinosa and Obama spoke as they returned to the Nationals' dugout to applause.
"I had fun," Espinosa said. "I said we'd love to have her and the president come out to some games and support us. I just said no Chicago hats next time."
President Obama pulled a White Sox hat out of his pocket before delivering the first pitch on Opening Day 2010. While this day was all about military families, the first lady took an opportunity to compliment Espinosa on the Nationals' play.
"All she said was: 'You guys have done a great job, and we've seen that you guys have really started to make some things happen,'" said Espinosa, who learned he would catch the first pitch three days ago. "A couple compliments, which was nice."
Espinosa was one of five Nationals players, along with Ivan Rodriguez, Drew Storen, Jayson Werth and Ryan Zimmerman, featured in public-service announcements drawing attention to Obama's "Joining Forces" initiative.
The campaign targets three aspects of military-family life -- employment, education and wellness -- which it hopes will result in improved resources through anything as large as a self-organized volunteer event to as small as a text message of support.
The Nationals actively participate on the largest scale.
Players and coaches regularly visit wounded service members at Walter Reed Army Medical Center in Maryland. And they often pause during warmups to applaud and honor veterans during the third-inning tribute.
The "Joining Forces" initiative hopes to draw attention to the difficulty of being a child in a military family, which often forces relocation and can result in loneliness or isolation.
The club realizes that and attempts to provide an escape for military families.
The Nationals partnered with the "Me and a Friend" program to provide tickets to children of active-duty service members for every Sunday game. They also provide tickets to the "Tragedy Assistance Program for Survivors" group, which offers resources to those affected by the loss of a loved one in military service.
This was not the first time the Nationals welcomed someone actively involved in spreading the word about veterans and military families to the park.
They feature five games in a Patriotic Series, and brought veteran Troy Yocum to the park on Memorial Day. Yocum is hiking across the country to raise money for military families, and everyone at Nationals Park on Memorial Day learned why.
"Today on Memorial Day -- a lot of people start thinking about our veterans," Yocum said. "What I want them to do is think about them all the time."
By "Joining Forces" with Obama's initiative, the Nationals proved they do.