continue that to WWI where millions died

Strange you should suggest that soldiers died of neglect, when the British medical services lost a mere [7%] (http://www.longlongtrail.co.uk/army/some-british-army-statistics-of-the-great-war/) of those in their care to wounds. Similarly, while close to 2 million out of 8 million casualties suffered by the French died, the rest were listed as wounded and probably enjoyed at least similar survival rates to British wounded. The war saw important developments in the medical arena, notably the widespread use of x-rays, the rapid development of plastic surgery, and the discovery of blood types and subsequently safer and more successful means of blood transfusion. The connection through letters to troops on the frontline was of vital importance to both soldiers and civilians, while in the British case both Sir John French and Sir Douglas Haig took an interest in the leisure and extracurricular activities of the soldiers of the BEF.

Edit: Just to add to the British case, [of 22 000 doctors in Britain when the war broke out, half would serve the military and of those 1000 would die] (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1079301/). It's interesting also to note, that the only British and Empire individual to win the Victoria Cross twice during the Great War was Medic Noel Chavasse, who was awarded the VC for 'conspicuous gallantry' while recovering wounded at the Somme, and was then awarded it posthumously for similar deeds at 3rd Ypres/'Passchendaele.'

As to when it became "fashionable," care for one's soldiers was always seen as a positive characteristic of any general, and the loyalty that could be engendered could prove a dangerous thing, as can be seen by the role played by the Roman Army in the politics of the Republic and Empire. In a modern sense, concern for the "common fighting man" probably achieved greater notice in the 19th century, with the proliferation of conscript and 'mass armies' in general. Drawing men from many parts of society together in turn created ties to the nation/state/country and thus added or increased the importance of the element of the 'home front connection.' However, again, such sentiments of care for the common soldier can be seen throughout history; Les Invalides began as a refuge for French former soldiers, initially the veterans of Louis XIV's wars.

I'd be interested to know the context of the biography and quote -- certainly there were times when Napoleon's adventures carried him into places quite far away from anything resembling hospitals, and the conditions of a Napoleonic battlefield right after a battle were gruesome. That said, though, it would probably be a mistake to assume that Napoleon's campaigns or his treatment of his soldiers was any sort of a linear progression from previous militaries.

Moving to something I actually know about, and not just speculating about your readings: The English navy started a specific fund to care for injured and disabled seamen in 1590; called the Chatham Chest for the, well, large iron-bound chest it was kept in, it was meant to offer lump sum and annual payments to disabled seamen. It was originally established around 1590, likely by Charles Howard (the first Earl of Nottingham, as well as Lord High Admiral of England during the Armada), to help sailors injured in the Spanish war.

The chest functioned as a pension scheme for disabled seamen. Every sailor in the Navy paid into it 6d per month (after 1649, surgeons and chaplains paid 8d and 10d), and it disbursed annual payments to wounded men based on their injuries -- rates varied over time, but they could be as low as £6 for loss of a limb or up to £15 for loss of two limbs, plus immediate money when the sailor sustained the injury (or, realistically, when he was injured, lived, and applied for relief).

The chest, being a strongbox of money kept at the main naval yard, was sometimes stupendously mismanaged; we know for example that Sir Sackville Crowe, Treasurer of the Navy from 1627-29, "borrowed" £3,005 from the chest which was never repaid, even after he was sued for the money. (To be fair to Sir Crowe, during James' reign the navy was strapped for cash; many men had their pay in arrears for six years or more.) But, it was meant to function as a relief for the "common sailor" and did so, with varying degrees of success, until 1803 when it was merged into a similar pension scheme at the Greenwich naval hospital.