Humanitarianism is the idea that all Humans have innate Value. All Humans have innate Rights, some of which are inalienable. The ideology existed for at least 4 millennia, but it became particularly popular among top thinkers during XVIIIth and XIXth centuries.
One of the first achievements of Humanitarian ideology was the abolition of cruel punishments during 1750 -- 1900 time frame. In 1750, torture and Capital Torture were routine in Europe, Colonial America, and Worldwide. By 1900, torture has been abolished and penal systems became much more humane. President George Washington and President Thomas Jefferson strongly believed in Humanitarian Values and Inalienable Human Rights -- the first ten Amendments were signed by them. Unfortunately these great men also had great flaws -- their ownership of slaves went against their principles.
Many nations returned to cruel punishments during 1930 -- 2018 time frame. First, Communist Nations introduced harsh penal systems with long prison terms and massive incarceration. Since 1990s, USA adopted similar system, and now several other nations including Brazil are following USA.
One thing Humanitarians tried to achieve globally, but achieved only on very small scale is Universal Welfare. Under Universal Welfare, everyone would have a right to food, shelter, and medical care of reasonable quality. Universal Welfare was a part of Jewish communities for 3,300 years -- the community was obligated to support poor members. In the late XXth century, Scandinavia developed a Welfare system which provided reasonable quality of life to people who could not or did not work. Universal Welfare greatly reduces crime and drug use.
Humanitarian policies follow from the idea that all Humans have inalienable innate value. Even the worst criminal has Constitutional Rights. A person who is 100\% law abiding, but is unable to provide for him/herself should have many more rights. In Scandinavia, even the worst criminals are housed in very humane prisons. People whose only crime is inability to earn money have many more rights -- and in Scandinavia they do get the support they deserve.
In modern USA, both Liberals and Conservatives have many opponents of Humanitarian ideas. Many Liberals support Identity Politics rather then Humanism.
Many Conservatives support Social Darwinism. Darwinism does not consider Humans innately valuable -- some Darwinists believe that Humans are highly evolved animals. One of the ideas of Darwinism is Survival of the Fittest. Some Darwinists believe that Society has little or no duty to help "non-productive" members.