Academically, he qualified in sports sciences from the Charles University in Prague, before becoming a professional soldier and reaching the rank of captain.

Jansa has been one of Czechoslovakia's and then the Czech Republic's leading players for many years, collecting experience across a range of chess activities.

The opening, distinguished by an early c6, offers the player of the black pieces the opportunity for greater flexibility, in order that an appropriate plan can be formulated, once white's strategy is revealed.

In international tournaments, he has been many times a winner, taking outright or shared first prize at Cerveny Kostelec 1959, Prague 1968, Madonna di Campiglio 1973, Amsterdam 1974, Vrnjacka Banja 1981, Trnava 1982, Borgarnes 1985, Gausdal 1987 (and third in 1988), Badenweiler 1990, Munster 1992 and Lazne Bohdanec 1997.

Jansa won the 2018 World Senior Championship in the 65+ category, edging out Yuri Balashov on tiebreak score.