訓 さかのぼ(る) ・ 音 ソ,サク
漢越音: tố
The walking radical 辶 with 朔 (the start of the month): walking back to the beginning, going upstream.
Stroke data: KanjiVG (CC BY-SA 3.0) — kanjivg.tagaini.net
歴史を百年遡る。 (れきしをひゃくねんさかのぼる)
We go back a hundred years in history.