What is the ruling on pondering at military heroes' memorial stones?

If the commemorative stones refer to the relics of disbelievers from previous nations, then it is not permissible to stand by them, nor even to enter them, except by passing through with humility, weeping, and contemplation.

However, if they refer to visiting the graves of heroes who sacrificed themselves to uphold the word of Allah, then one should follow the guidance of the Prophet, peace be upon him, in visiting graves to supplicate for them and seek forgiveness for them, while saying: "Peace be upon you, inhabitants of these dwellings, from among the believers and Muslims. And indeed, Allah willing, we will join you. We ask Allah for well-being for us and for you."

It should be noted that it is not permissible to build upon a grave a monument, a shrine, or anything else, as the Prophet, peace be upon him, forbade that.