The Chechen birth rate rn is actually pretty low.

For the past 10-15 years, Chechnya has boasted one of the highest birth rates in Russia, and one of the lowest mortality rates, resulting in steady population growth (1.8 percent in 2015) considerably higher than that of the country as a whole.

Consequently, according to official statistics, Chechnya’s population has grown from 1.205 million on January 1, 2008 (a figure some analysts consider implausible) to 1.269 million at the time of the October 2010 Russia-wide census and 1.391 million in November 2015.

At least half that population is under 30 years of age.

At the same time, the number of children born in Chechnya rose from 25,800 in 2004 to a record 36,532 in 2009. Since then, however, the number of births has declined, to 34,770 in 2012 and 29,498 in 2015. And, during the first six months of 2016, the birth rate fell by a further 6.9 percent, the steepest decline of any region in Russia.

Now, the article:

Medieval Europe was able to recover from devastating wars and plagues, and a life expectancy rate of around the age of a postmodern grad student, because of high birth rates.

That's kinda just why the Chechens did.

Germany went into WWI fueled by an aggressive birth rate of 3.5.

The Germans: used to even fuck aggressively.