The protected emblems

the only marks with an army behind them

Unicode: U+271A heavy greek cross · U+262A star and crescent — the emblems as such are not encoded
Meaning: Protection under the law of armed conflict. The emblem does not describe a service; it confers a status.
History: The 1864 Geneva Convention adopted the Swiss flag with its colours reversed, in honour of the host state, and declared the mark free of religious meaning. That declaration was not accepted: the Ottoman Empire objected in the 1870s and used a red crescent, formally recognised in 1929; Iran used a red lion and sun until 1980, and the emblem remains reserved though dormant; and in 2005 Additional Protocol III created the red crystal, a form with no religious reading at all. Four emblems exist because the neutrality of the first was asserted rather than achieved.
Variants: Cross, crescent, crystal, and the dormant lion and sun. The crystal may frame another emblem inside it, which is how the protocol resolved a forty-year impasse without ruling on anyone’s symbol.
Related: ⚕ ☤ the medical marks (SYM·0002, SYM·0005) — none of which confers protection; the working and legal reading at Visual Grammar, VG·0010.
Appears: Field hospitals, ambulances, aid convoys and protected buildings; and, in violation, on first-aid kits, pharmacies and game interfaces worldwide.
Evolution: A national flag inverted → a treaty emblem → four emblems, one dormant, and a permanent argument about whether a designer can declare what a mark means.

Sources · 4

documented The Geneva Convention of 1864 and the adoption of the reversed Swiss flag.
documented The formal recognition of the red crescent in 1929, the reserved status of the red lion and sun, and Additional Protocol III (2005) establishing the red crystal.
documented The prohibition on perfidious use of the emblems under international humanitarian law.
documented The Unicode Standard: U+271A is a typographic cross, not the protective emblem, which has no encoding.