explain what is meant by the cult of manliness?

It is an ideal of physical and moral courage. As proposed by the Victorian school reformers like Dr Thomas Arnold young men should be prepared to face challenges fearlessly whether on the sporting field, or later perhaps on the battlefield, but equally importantly face moral challenges, be prepared to stand-up to the bully, never lie or take the easy way out, show good judgement. A 19th century knightly ideal. Although Arnold and his followers would have thought that moral courage was the most important kind as the idea developed it became more about physical prowess and courage. In Britain boys were urged to show the "John Bull spirit". By the late 19th century there was a vogue for physical development. For the first time since the Greeks and Romans gymnasia appeared across Europe and North America. Men liked to "prove" themselves by taking part in sports, climbing mountains or taking long treks, and often by shooting as many animals or birds as they could. Englishmen liked to box, Germans preferred scarring one another in epée duels (real swords not foils).

In the USA Teddy Roosevelt, a sickly youth, tried to build up his strength in adulthood, boxed, hunted and took a moral high tone with all his opponents from the gangs of New York to the Spanish Empire.