Lev Semenovič Pontryagin was born in Moscow, Russian Empire, on September 3th, 1908, i.e. 105 years ago, and died in May 80 years later, about 25+ years ago.
Interestingly and sadly enough, a primus stove explosion made him legally blind at the age of 14. That didn't prevent him from becoming a top mathematician.
On the other hand, it didn't stop him from being a jerk of a sort, either. In 1936, he warned the Soviet officials that the mathematics community was full of counter-revolutionaries in the so-called Luzin affair. People were losing jobs. He was not only an aggressive commie, he was a sort of fascist, too. During mathematical conferences, he would scream that a pro-Israel Jewish scientist named Nathan Jacobson was a mediocre mathematician and racist because he was a Zionist. Another, even better Jewish mathematician, Grigory Margulis, won the Fields medal but couldn't get the permission to leave the USSR after Pontryagin painted him as a dirty Jew, too.
Much like other anti-Semites, he would claim that he wasn't one – he was just an anti-Zionist, everyone was told. Good try but my suspicion isn't quite gone (although I made a different conclusion 5 years ago).
Later in his career, he would work on optimization; Pontryagin's minimum principle is behind the bang-bang control. But string theorists primarily know him because of his earlier work on algebraic and differential topology.
Needless to say, the most famous concept named after him is a characteristic class now known as the Pontryagin class. (Although the Pontryagin duality for the Fourier transform on locally compact groups is also deep.) If you search through Google Scholar for papers mentioning both "string theory" and "Pontryagin class", you get 276 hits dominated by papers written by Witten, Vafa, Harvey, Moore, Sethi, Mukhi, and a few pals.
The Pontryagin class is a complexified even Chern class within a cohomology whose degree is a multiple of four. Needless to say, I don't really understand these matters well. The people for whom it's their cup of tea must think about many things in terms of vector bundles. It's probably great for them and it allows them to see and calculate many interesting things but despite a course by GM, I just couldn't learn to use those things. I need to translate bundles to some fields with some properties or physical conditions, otherwise I don't really understand them. In some sense, I feel that mathematics and not physics must be the "mother tongue" for those folks even though many of them are stellar theoretical physicists, too.
A longer CV was written 5 years ago.