I would respond that the fact of my son choosing to be in harm's way (and he did choose it) changed nothing for me; I have long been comfortable with the fact that protection for my loved ones can only come from God and not from any effort (or worry) of mine. The dangers my son faces may seem more imminent, but witness the tragic events that can occur "at home," such as the Virginia Tech shootings a year ago. What, or better, where is safe?
It would be a lie to say I did not worry, but my faith in Jesus Christ and trust in God's sovereignty have allowed me to be at peace with the circumstances of life, even if and when I don't understand the events that occur. Even if tragedy struck, I would want my response to be to praise and thank God for his grace and love.
Benjamin B. Warfield said,
A firm faith in the universal providence of God is the solution of all earthly troubles.
Some might hear that and say, "Well, you don't understand my problems!" or "You'd be saying something different if..." Warfield understood; his wife was paralyzed soon after their marriage. Even so, he cared for her throughout their 39 years of marriage, and he remained a yielded, faithful servant of God. Read about him here.
Today, I praise and thank God for protecting my son, who I spoke with last night. He is back in this country, this tour of duty coming to an end, and he should be home this weekend. So, from just another human father to the one Father of all, who loves me as if there were no other, so much that he didn't spare his own son, and indeed he loves all with that same boundless love, praise and glory to you, Lord.