Mission 5: Forget about that captain whatever to tell you use missile, IGNORE HIM. Build 2 outposts you will be fine. Stock up resources using outpost to generate manpower, when attack wave come push out tanks from both of them (if enemy only have air, use rifle to defend instead).
Mission 6: Watch the enemy units, and remember the ROCK PAPER SCESSIORS (practice in quick play hard-hard mode) First ring: rifleman > scout > tank > rifleman Second ring: MK II > air unit > sniper > ground units Third ring: roman > sniper > tank > roman
Tank is the counter to mass ground units MK II is the counter to mass air units
Roman is an excellent unit to absorb damage, allowing your more expansive units (tank, MK II, nighthawk, queen) to hail down the enemy.
Mission 5 used to be unable to build forge and there were very few influence units (only the special ops, modified phantom and modified sakata, these costed 100 influence back in the day, and missile silo did not produce influence). With so many updates after the game has changed entirely.
It is very easy to beat mission 5 when you can use forge.
