Judith, I'm a hobbyist and not an expert, but here is some info I found online, and a couple of suggestions on further research:
It appears he is listed in the National Archives WWII Honor List of Dead and Missing Army and Army Air Forces Personnel as Dolphin, Howard F., serial number 17170453, Private First Class, KIA (killed in action). This listing is in the casualties from Delaware County, Iowa. The first digit in his serial number being a 1 indicates he joined the service, rather than being drafted.
You may be able to get his personnel record through the NPRC in St. Louis. (They had a disastrous fire in 1973 which destroyed many records, but it is worth a try.) Info on that resource can be found at this web page: http://www.archives.gov/st-louis/military-personnel/index.htmlhttp://www.archives.gov/st-louis/military-personnel/index.html
You can also send for his Individual Deceased Personnel File (IDPF). As others in this forum have addressed, the info found in an IDPF can be graphic. If you pursue this resource, you should be prepared for that possibility. Send your request to: US Total Army Personnel Command ATTN: TAPC-PAO (FOIA) 200 Stovall Street Alexandria, VA 22332-0404 Be sure to cite the Freedom of Information Act in your request.
Some guidance on how to proceed with any info you acquire from these sources can be found at this site: members.aol.com/dadswar