If your spouse leaves you for a continuous period of two years or more, this is desertion. However, desertion is not much relied upon as grounds for divorce because it can be difficult to prove if it is disputed by the partner who allegedly deserted.
In the event that your spouse says something like: "I'm leaving you", and walks out, intention to desert can be more easily proved. However, your spouse might say nothing and simply go to work overseas for a period of two years. This may or may not be desertion.
If your spouse had no intention of never returning at the moment of leaving, this would qualify as a period of desertion. Having said that, your partner may not have decided to never return until they had been absent for a year. In this latter case they could only be considered to have been in desertion after this decision had been made. As a result, this can be very difficult to prove to the court’s satisfaction.
Instead, it is possible to seek a divorce within six months of the departure on the grounds that it was unreasonable behaviour to leave for an overseas job without consulting the partner left at home. However, every case for desertion is different, and if the divorce is likely to be contested, it is prudent to consider how other possible grounds for divorce apply to your case.