Sahabas left Makkah and Madina to preach Tawheed around the globe

W-Salam Wa Rahmatullahi Wa Barakatuh,

I am looking at your question differently.

When I look (ponder) over the Qur'aan, I understand that the methodology of our beloved Nabi (Sallallaho Alaihe Wassallam) was Dawah towards Allah (SWT).

[12:108] Say, This is my way. I call (people) to Allah with full perception, both I and my followers. Pure is Allah; and I am not among those who associate partners with Allah.

Imam Ibn Katheer (RA) states that Allah (SWT) is ORDERING Nabi (Sallallaho Alaihe Wassallam) to inform manking and Jinnkind that his way (path), methodology, Maslak and Sunnah is to give Dawah towards Allah (SWT)

يَقُول تَعَالَى لِرَسُولِهِ صَلَّى اللَّه عَلَيْهِ وَسَلَّمَ إِلَى الثَّقْلَيْنِ الْجِنّ وَالْإِنْس آمِرًا لَهُ أَنْ يُخْبِر النَّاس أَنَّ هَذِهِ سَبِيله أَيْ طَرِيقَته وَمَسْلَكه وَسُنَّته وَهِيَ الدَّعْوَة إِلَى شَهَادَة أَنْ لَا إِلَه إِلَّا اللَّه وَحْده لَا شَرِيك لَهُ يَدْعُو إِلَى اللَّه بِهَا عَلَى بَصِيرَة مِنْ ذَلِكَ وَيَقِين وَبُرْهَان وَكُلّ مَنْ اِتَّبَعَهُ يَدْعُو إِلَى مَا دَعَا إِلَيْهِ رَسُول اللَّه صَلَّى اللَّه عَلَيْهِ وَسَلَّمَ عَلَى بَصِيرَة وَيَقِين وَبُرْهَان عَقْلِيّ وَشَرْعِيّ , وَقَوْله " وَسُبْحَان اللَّه " أَيْ وَأُنَزِّه اللَّه وَأُجِلّهُ وَأُعَظِّمهُ وَأُقَدِّسهُ عَنْ أَنْ يَكُون لَهُ شَرِيك أَوْ نَظِير أَوْ عَدِيل أَوْ نَدِيد أَوْ وَلَد أَوْ وَالِد أَوْ صَاحِبَة أَوْ وَزِير أَوْ مُشِير تَبَارَكَ وَتَقَدَّسَ وَتَنَزَّهَ وَتَعَالَى عَنْ ذَلِكَ كُلّه عُلُوًّا كَبِيرًا " تُسَبِّح لَهُ السَّمَوَات السَّبْع وَالْأَرْض وَمَنْ فِيهِنَّ وَإِنْ مِنْ شَيْء إِلَّا يُسَبِّح بِحَمْدِهِ وَلَكِنْ لَا تَفْقَهُونَ تَسْبِيحهمْ إِنَّهُ كَانَ حَلِيمًا غَفُورًا" .

Imam Tabari (RA) mentions that he Nabi (Sallallaho Alaihe Wassallam) was COMMANDED to say that his duty is to give Dawah towards pure Tawheed, sincerity (towards worship) with rejection of all other dieties and dogmas, and towards obedience of Allah (SWT) and abandoning of disobedience towards him and that this is his path and his invitation (to others)...

Sayyidina Rabi Ibn Anas (RA) stated in regards to [12:108] Say, This is my way. I call (people) to Allah with full perception, that this is MY DAWAH!

Sayyidina Ibn Zayd (RA) stated in regards to [12:108] Say, This is my way. I call (people) to Allah with full perception, that this is MY WAY, MY COMMAND, MY SUNNAH and MY MANHAJ

Both of these are ascribed to Nabi (Sallallaho Alaihe Wassallam) implicitly.
 

الْقَوْل فِي تَأْوِيل قَوْله تَعَالَى :

قُلْ هَذِهِ سَبِيلِي أَدْعُو إِلَى اللَّه عَلَى بَصِيرَة أَنَا وَمَنِ اتَّبَعَنِي وَسُبْحَانَ اللَّه وَمَا أَنَا مِنَ الْمُشْرِكِينَ

So it is inconceivable for us to imagine that the Sahabah did anything apart from establishing the Tawheed of Allah (SWT)! When you look at Jihad the most conclusive verses of its purpose are as follows:

[2:193] Fight them until there is no Fitnah any more, and obedience remains for Allah. But, if they desist, then aggression is not allowed except against the transgressors.

[8:39] And fight them until there is no Fitnah (mischief), and total obedience becomes for Allah. So, if they desist, then, Allah is indeed watchful over what they do.

Imam Ibn Katheer (RA) Allah commands us to fight the kuffaar so that there will be no fitnah, i.e., shirk, and the religion will all be for Allah alone, i.e., the religion of Allaah will prevail over all other religions. 

"أمر تعالى بقتال الكفار حتى لا تكون فتنة أي شرك ويكون الدين لله أي يكون دين الله هو الظاهر على سائر الأديان"

Imam Tabari (RA) So fight them until there is no more shirk, and none is worshipped except Allaah alone with no partner or associate, and trials and calamities, which are disbelief and polytheism, are lifted from the slaves of Allaah on earth, and religion is all for Allaah alone, and so that obedience and worship will be devoted to Him alone and none else.  

فقاتلوهم حتى لا يكون شرك ، ولا يعبد إلا الله وحده لا شريك له ، فيرتفع البلاء عن عباد الله من الأرض، وهو الفتنة ويكون الدين كله لله ، وحتى تكون الطاعة والعبادة كلها خالصة دون غيره

[QUOTE=Imam Ali] In adabah gasht there is always references made how all Sahaba (RA) had this concern for the Ummah and made preaching Tawheed their primary goal as there are no Prophets to come after Mohammed (SAW).[/QUOTE]

It can be safely deduced that preaching Tawheed was their primary goal and the best methodology was adopted but the overall goal was Tawheed, yes.

What is the purpose of Jihad, not spreading Tawheed?