Also known as "serviceperson's will".
The Romans, civil law adherents that they were, formalized the solemnity of making a will. This was partly to ensure that as the primary person would be deceased when the document might later be called into question, there would be other procedural safeguards in place.
The common law began its foray into privileged wills when, in 1837, England had enacted its English Wills Act which extended it to "any soldier being in actual military service or any mariner or seaman being at sea."
From that evolved a whole series of requirements, varying, to this day, from jurisdiction to jurisdiction including, for example, the requirement of a will being signed by a person of the age of majority, hand-written, type-written, notarized, witnessed, dated, signed or registered, or a combination thereof.
To privilege military personnel and mariners, who faced particular hazards daily, the law was relaxed as to them by allowing their wills, even if only made orally (but in this latter case, a witness was required).
Initially, too, such a privileged will could only dispose of chattels - not real property. But that limitation was eventualy relaxed.
In Feeney's Canadian Law of Wills, 4th Edition (2007):
"These informal wills, if good when made, remain perfectly valid when the serviceperson leaves the service and lives many years oif civilian life before death."
Almost all Canadian provinces allow privileged wills for members of Canadian Forces "while ... on active service", or a mariner or seaman, when at sea.
Typically, all that is required of these wills is that they be in writing (hand or typed) and either signed by the testator or signed by another at his direction and in his presence.
A September 2007 study by the Alberta Law Reform Institute entitled The Creation of Wills offers the opinion that in regards to Newfoundland, Labrador and Nova Scotia, as these latter provinces defer to the common law and on that basis, simple oral privileged wills arevalid for fishermen, sailors, mariners and soldiers.
The law in the United States and Australia is a patchwork. New Zealand limits their validity to twelve months..