OKLAHOMA CITY (AP) Oklahoma's adjutant general challenged those attending a Memorial Day service on Monday to begin their summer by visiting the graves of fallen soldiers and thanking veterans for their service.

Maj. Gen. Myles Deering spoke at an annual ceremony held at the Oklahoma National Guard's 45th Infantry Division Museum, one of a handful of Memorial Day-related events being held in the state.

"We remember that soldiers served and some died to preserve our basic freedoms," Deering told a crowd of about 600 people, encouraging them to "honor them and look to them for guidance. We should imitate their courage, sacrifice and excellence."

The 40-minute ceremony began with a flyover of a military helicopter and the firing of a World War II-era tank gun, followed by a parade of military flags. As the flags passed by, veterans and soldiers in the audience saluted, while young children held their hands over their hearts.

Deering said that veterans have seen the cost of freedom and have borne that cost themselves.

"Today soldiers give up the comforts of home so Americans can go about their lives," he said.

After recounting totals of U.S. war dead in World War II, the Korean War and the Vietnam War, Deering said that some things are worth fighting for, including freedom.

"War is ugly," he said. "But a man without principles will never risk death to secure his own freedom, much less anyone else's."

At the ceremony's close, a bugler played "Taps" as a wreath was placed at the base of a U.S. flag that flew at half-staff in honor of those who have died while serving their country.

Similar events were held throughout Oklahoma on Memorial Day, which has been observed since the 1860s and was declared a national holiday in 1971.

At Fort Sill, a service included a 21-gun salute and remarks by the southwestern Oklahoma Army post's commander, Maj. Gen. Peter Vangjel.

In Tulsa, veterans and others gathered at Memorial Park Cemetery for a retirement-of-the-colors ceremony and the laying of wreaths, while ceremonies marking the holiday also were held at national cemeteries near Fort Gibson and Elgin.