D.G.
Hi M.,
First of all I'd like to say I'll pray your husband and your family that you will get through this time with grace and comfort.
Second, three year lil people are quite literal. If you say the sky is blue, they look up to see the blue sky. Three years old lil people are also very observant. She knows there are people fighting far away (and now Daddy is going there) and people die and never come back. Have you and Daddy sat down with your daughter and told her Daddy is going to be gone for a little while, but when he's done, he'll be back. Make it fun for her. Tell her we'll write him, and you can make special cookies for daddy or we send special presents to him. Even if she's clinging, get her involved in the process. If it's hurting her she knows it's hurting you too. And you must tell her Mommy will stay here while daddy is gone and I won't leave you, but if I do have to go somewhere or drop you off at school, I'll be back to pick you up. When Daddy comes home now, before he leaves, get her to hug him and say now you can put it in a jar and when you miss him, you can pull out a hug. So while he's here we must fill the jar all the way up. Basically, get her involved. She's going to be sad, but some of these things might help.
I hope some of this helps. And they do have Play Therapists you can send her too. They council with toys and drawing and playdo. God bless you and your husband and your daughter. Make sure you get a lot of support for yourself too.