What is the right timing for invading a moyo and how does one make sure that the invading stones are not captured by the opponent? The answer differs depending on the circumstances: the arrangement of the stones, the balance of territory, relative skill at settling stones etc. It’s extremely difficult to answer your question simply. One of the criteria for choosing the right timing is to invade the move before one extra move by the opponent would turn the moyo into definite territory and make the game a loss for you. If you invade too early, you just create a weak group that gets chased around the board and gets you into trouble; not only do your own positions suffer, you might end up having the invading group die on you. The opponent’s moyo may look big, but jealousy is taboo. It’s best to invade after, to some degree, fixing up your own territory and your shape. However, you must take care not to miss the best timing. How to avoid having the invading stones captured? H’m. If there were a secret formula for this, I’d like to know it myself. The opponent will go all out to capture you, so things won’t be easy. The knack is to play lightly and flexibly in settling your stones, while taking advantage of aji and thinness in your opponent’s position. The most important thing is actual experience, I think, but studying sabaki (how to settle weak groups) with books would also help.