This is the best way to prevent a leader rush.

If you are playing as UNSC DO NOTupgrade flamethrowers.

If you are playing as Covenant upgrade jackals.

ANT-WARTHOG RUSH

Professor Anders is the best character to beto prevent a warthog rush.

Create an army of Gremlins (out of base).

Takea rebel base when you have around 8 up.

Upgrade them completely when you have about 20 up.

This willALWAYS beata warthog rush.

Another way is with theCovenant.

Usingyour leader of choice create an army of infantry.

Make plenty of hunters and upgrade them as well.

If attacked by warthogs but you do not have enough units to counter attack it may be wise to build jackals.

The warthog rusher could build flamethrowers to easily kill your hunters so building jackals will counter that.